Frequently Asked Questions

The F.A.Q. section contains some common questions related to home improvement projects, along with expert answers.

Air Sealing Tips

Dear Harold,

What do you recommend for sealing the little gap between floorboard and wall at the baseboard?  Our place has a cool draft coming through there and I’d like to get rid of it.  Any pointers appreciated.

Roy E., Cambridge, MA


Expert Answer:

Dear Roy,

Caulking of baseboards and around windows is an easy way of making your home less leaky and keeping your expensive conditioned air inside.  It also makes your home more comfortable by making it less drafty.

Frequently, caulking is part of the comprehensive air sealing of your home which can be included as part of an energy audit or a professional weatherization.

While caulking is somewhat tedious, it is an easy job for a homeowner to do.  There are many different types of caulks to use; generally you probably want a paintable, silicon clear or translucent caulk.  Some brand names include DAP and Phenoseal.

Attic Insulation

Dear Bruce,

I recently had an energy audit done to my 1850s era shingled house.  The auditor recommended adding insulation to the walls.  Because the house is so old, I had to run this by the town’s historical commission, and they have rejected the permit on the grounds that blowing insulation into the walls will cause moisture issues and damage the house.  What can I do to get better energy efficiency?

Alida F., Cambridge, MA


Expert Answer:

Old houses, like brand-new houses, operate as a system.  Since your house was built before 1950, you should keep in mind that it probably wasn’t designed with much if any insulation–the attic and wall cavities, indeed the whole shebang, “breathes.”  Insulating can slow down that breathing, which will indeed keep more warm air inside, but you have to be very careful to not let the moisture in that air get trapped in places where it can do harm–like up against wood, where it can initiate rot, or inside spaces where mold can take hold.

Since insulating walls involves poking holes in them, and the historical commission has issues with this, I think it’s important to first see what other, less-intrusive measures could be taken.  You’ve already had a proper energy audit, which includes a blower-door test and the use of a thermal-imaging camera.  That’s what should have shown you where the biggest energy losses are occurring. However, it would be my guess that it’s probably not your old windows and walls.  More likely the house needs a good air-sealing, with simple solutions like weatherstripping windows and doors, closing chimney and fan dampers, and caulking gaps in the basement and attic. Then make sure your heating plant is cleaned and operating properly and basement pipes insulated.  After that, it’s a question of payback calculations on things like new storm windows, more efficient heating and cooling equipment and, yes, insulation.  With any luck, your energy audit company prioritizied such tasks for you in terms of payback and complexity.

If it were my house, and insulation was deemed to be on the to-do list, I’d make sure to follow my mom’s advice and put on a hat.  Heat rises, and where much of it goes, the attic, is usually easy to insulate.  Start with that and see how your energy bills respond.

Energy Incentives

Dear Harold,

I have heard about some incentives available to me if I install energy efficient home improvements–rebates and tax credits.  But I’m not sure how these work.  Can you explain?

Ralph L., New York, NY


Expert Answer:

Dear Ralph,

Of the various incentive programs that help you to make you home more energy efficient, the majority of them come in one of two flavors, either as a tax credit or as a rebate.  So what’s the difference?

While both are real money, the biggest difference is when you get the money.  Rebates come to you anywhere from immediately to up to a number of weeks after the purchase.  With a tax credit you get your money after you file your taxes, so for some of you that may be soon after April 15, while for the slackers among us (like me) it is even later.

Here’s how they work:  a rebate will return to you some portion of the purchase price of a product or service.  For example, if there is a $2,000 rebate on insulation, once the insulation is installed and the paperwork showing evidence of the installation is done, the dollars come back to you directly.

A tax credit is a little bit more cumbersome.  If you purchase an approved product or service, for example a new geothermal HVAC unit, you fill out a government form (IRS Form 5695) that allows you to cut the amount of taxes you owe by some amount that is directly linked to the cost of your energy efficiency upgrade.  For geothermal energy, the government offers a tax credit for installing a geothermal system that’s equal to 30 percent of the cost of the system.  This amount is then deducted directly from your tax bill.  If the geothermal system costs $10,000, 30 percent is $3,000, so the amount you have to pay the government is reduced by $3,000.  For some this means writing a smaller check when you file your taxes, for others it may mean a tax refund.  Either way it is real dollars.

You may also run across special offers or coupons that reduce the price of, say, an energy efficient appliance.  These work the same way as they do in any retail store–you present the coupon or special offer and the amount is deducted from the total cost of the appliance.


Does Green Spray Foam Exist?

Dear 360Chestnut,

We will be redoing our kitchen soon. We now have cellulose in the walls. When we gut the room, I want to insulate with some kind of spray foam insulation. I’m concerned about off-gassing. Are the soy-based or “greener” spray foam insulations any better?

Monica, Quincy, MA


Expert Answer:

Dear Monica,

Off-gassing is generally not a particularly big issue with foam insulation. Out of all the products you will put into your new kitchen, the insulation off-gasses very quickly and then is done. As a result, the day you insulate with foam you want to be out of the house for 24-48 hours due to a terrible smell.  After it is over, there is very, very little off-gassing over time (zero volatile organic compounds once the insulation has cured).

The “green” soy based products are only marginally green.  I think only about 7% is soy or castor oil with rest petroleum based like all other foams. Thus, from a green perspective it really doesn’t matter that much which you use.

If you are concerned about off-gassing in your kitchen, I would be careful to use low/no-voc paints, adhesives and floor finishes.  I recommend a water-based finish on your floor.  Also, consider using non-formaldehyde plywood in your walls.  Those things will make more of an impact than green foam insulation with regard to off-gassing.

The application that you are talking about – gutting your kitchen and getting all the way down to the studs — is perfect for damp-sprayed cellulose. Damp-sprayed cellulose  shoots from a gun while slightly damp, which allows the insulation to stick to the bays and pack very densely. After applied, studs shave off the cellulose evenly making dry wall easy to install. In this application, you do not install the walls first.

This results in an r-value (the measure of how well it insulates)  that is about the same for cellulose and open cell foam (~3.5).

Between open cell foam and cellulose, which is better?  It depends on what your major concerns are.  If your home comprises of old construction with many holes/penetrations in the shell of the building, or you live in a particularly windy area (few neighbors, along the ocean, that sort of thing), you should probably go with open cell foam.  If green is a high priority for you, cellulose is the answer as it has about 1/10th the embodied energy as foam.  Generally, cellulose is going to be far cheaper then foam of any kind.
Another possible insulation is closed cell foam which has an r-value nearly twice open cell foam or cellulose.  Closed cell foam is great stuff; however, it is very expensive and stiff.  So if it expands beyond the bays, then it can’t be shaved off so easily.  Also, closed cell off-gases more than open cell and uses even more embodied energy to create.

That said, if you want to go crazy you could do a thin layer of closed cell followed by damp-sprayed cellulose (or even fiberglass) to bring it even to the studs.  (Sometimes this application is called “Flash & Batt”.)    If money and green are no object that’s the way to go, but sort of overkill in my estimation.

Finally, as long as you got me started:  If applicable, insulate underneath your kitchen floor.  It will make it a lot more comfortable.


Using a Well for Geothermal


Dear Harold,

my main question is if I can connect the well water to a water furnace, and from there heat up the water radiators?

I hope you can guide me.


Edward, New Jersey


Expert Answer:

Hi Edward,

Let’s see if we can answer your question, though in the end the true answer will only come from a geothermal installer.

With the usual caveats that we haven’t seen your home, the short answer is that your existing well probably would not be able to power your geothermal system.  It simply will not have the volume to heat and cool your fairly large house (3600 sqft).  But here is what I like about your home and site: 2 acres!  That at least allows for the possibility of doing a horizontal geothermal system.  That said, here is what I don’t like about your home:  Radiators.  A forced hot water system can work very nicely with a geothermal system.  In fact, if cost is no objective, hot water is the system you want.  The problem is on the cooling side.  How are you cooling your house now?  If there is existing ductwork, great you can have the geothermal do both.  If you don’t have air conditioning now the numbers don’t work quite as well.  Generally speaking (again, big generalities here) the initial cost of installing a system to just heat your home (and not cool it) make the payback really difficult.  If you are planning on installing ductwork and central air anyway then geothermal is back on the table, particularly with the 30% Federal tax credit which is really nice.

Here is another option that we see frequently in Massachusetts: air source heat pumps which are also called ductless mini-split systems.  We have a lot on our site about them but in a nutshell it is a heat pump system that transfers the heat from the air either in to or out of the home whether you are heating or cooling your building.  They are very efficient.  The problem is they stop working when it gets very cold, less than 20 degrees.  For that reason you leave your oil system in place and run it on the coldest days of the year.

I particularly like ductless mini-split systems for big, old houses with each room being its own little climate zone – ductless mini-splits allow you to zone each room.  Plus the same unit heats and cools which is very nice.  Traditionally, the knock against mini-split systems was they were loud.  They are much quieter now.

The best strategy for you would be to price out both systems and see after tax credits where you end up.

If you don’t mind, we can connect you with both geothermal contractors and mini-split contractors.

Let us know if you have any more questions,

Harold Simansky

Green Insulation


Dear Bruce,

It appears that all thermal insulation products are green.  For that matter, any product that reduces heating and/or cooling loads are considered green.  Shouldn’t there be a distinction between these products as to how “green” they are?  Using enough energy to melt sand into glass and then spin it into fibers doesn’t make sense to me.

Fran B., Peabody, MA


Expert Answer:

Dear Fran,

In a nutshell, I would concur with your point that all insulation is green–it’s just about the best thing you can do to save energy in a house–and I would also agree that, given the alternatives, fiberglass insulation in general isn’t a very good choice. When it comes to insulation, fiberglass is the poorest performing insulation you can use. A few mistakes in installation, and its efficiency plummets. (Poor installation of fiberglass usually involves not filling the voids and/or overcompacting.)

And there are also health issues associated with fiberglass insulation. Fiberglass insulation packages are required by OSHA to display cancer warning labels. Direct contact with fiberglass materials or exposure to airborne fiberglass dust may irritate the skin, eyes, nose and throat.

Instead, I recommend sprayed polyisocyanurate foam or properly installed blown cellulose, which is made from 100% recycled newspaper.  You can also find soy-based spray insulation. These perform much better than fiberglass–filling the cavities completely, therefore doing a much better job of stopping air infiltration—and they don’t contain formaldehyde, common in many fiberglass products.

Horizontal & Vertical Geothermal Systems: Pros and Cons

Dear Ryan,

I’ve heard that when it comes to geothermal heating and cooling, there’s a technique called “horizontal boring” and another, “vertical boring.”  Can you summarize the differences and the pros and cons of each?

Dale W., Bismark, North Dakota


Expert Answer

Dear Dale,

In Boston, where 360Chestnut is based, we generally don’t do horizontal boring for a number of reasons that get to the heart of whether you choose a vertical system versus a horizontal system.

Here, most building sites are pretty constrained so there simply is not enough room to put in a horizontal system.  The idea of laying thousands of feet of pipe horizontally on a piece of land that could be as small as a few thousand square feet makes local contractors very nervous.  So in many cases, horizontal is a non-starter.  Also, even with plenty of space, New England has a lot of rock underground, and horizontal boring into rock requires special equipment, which translates to “very expensive.”

In the Midwest, horizontal boring to install geothermal loopfields is common practice.  Horizontally-bored installation methods give you access to areas where you wouldn’t otherwise have access (under parking lots, tree groves, lake beds, buildings, etc.)  Also, because the loops terminate on the same end of the field, it will reduce the amount of excavation required to run the supply-return lines into the building.

A few things to remember if you go for horizontal drilling are:

  • Soil properties are not generally as conducive to heat transfer due to shallower installation depths.  Horizontal loops can be designed to provide the same performance as vertical loops as long as the designer knows how to properly account for this.
  • You need a large amount of green space.  Although you don’t need to excavate from the surface to install the loops, a horizontally-bored GHEX (ground heat exchanger) will still require a large amount of land area.  Of course, you’ll want to stay within your property lines when installing these systems.
  • Grouting is of the utmost importance. While aquifers aren’t usually penetrated during horizontal boring, grouting is just as important in this application. While some soils will collapse completely around the u-bend piping in the bore, some soils will not. Grouting is the only way to guarantee the contact between the pipe and the earth that is necessary for proper heat transfer.

So, the short answer to which method you choose is, “it depends.”  Also, check out our geothermal resources.


How Can I Become a Geothermal Drilling Contractor?


Brian Hayden

Dear Brian,

I’m a class A well drilling contractor living in southern California but I also have ties to northern Virginia. I’m interested in becoming a geothermal drilling contractor in one or both places and am looking for any insight or advice you could give me.

Robert T., Lucerne Valley, CA


Expert Answer:

Dear Robert,
I know many drilling contractors who feel getting into the geothermal industry is the best business decision they’ve ever made.  The geothermal industry has experienced steady growth of about 30% per year through recent ups and downs in the economy.  It’s an industry that needs drilling contractors –especially good ones who know what they’re doing.

I suggest two first steps:
Try to quantify the demand in both California and Virginia to determine where to focus your effort.  You can do this by surveying existing customers, HVAC contractors, and any engineers that you know.  The mid-Atlantic market is much bigger than the California market, but there may be opportunities in both locations.  The easiest way to find business in the beginning will be to work as a subcontractor for a design engineer or contractor who is managing the project and needs a partner to install the ground loops.
Start learning as much as you can about the technology.  There is a lot of free information out there, and if your customer survey looks promising then you can invest in more technical training and certification.  The best sites for that are: GEO, the International Ground Source Heat Pump Association, and the geothermal section of HeatSpring Magazine.
Learning to be a great well driller is the hard part – adding geothermal to your business will be very easy in comparison.  I should warn you though: “geo-junkie” is a term used a lot among the geothermal industry veterans.  Once you start, it’s really hard to stop!

How Much Will a Geothermal System Cost?


Dear Harold,

I’m interested in geothermal heating and cooling.  How much would a system cost to heat/cool a house with approximately 1300 square foot? If the minimum cost of a system is $25,000, I don’t see how it would even pay for itself by the time you factor finance cost.

Maurice P., Lufkin, Texas


Expert Answer:

Dear Maurice,

You ask an excellent question that I would like to answer in two ways.

The first is purely by the numbers.  Does it financially make sense to transition to a geothermal system?  The answer is, of course, it depends.  It depends on what sort of rebate or incentives exist that you are eligible for, how much you are currently spending on heating and cooling, and how much it all costs.

Let’s take your $25,000 number and how this decision may play out.  If your geothermal system costs $25,000 you are eligible for a Federal Tax Credit equal to 30% of the cost, or $7500.  On top of that there may be utility and state tax credits that can be quite generous.  On average, this will knock off another 10% off the cost ($2,500).  So this $25,000 system now costs you $15,000.

In a number of states, there are interest free loans to install these types of systems.  It is not unusual to see a ten-year term on this loan.  In which case your $15,000 geothermal system ends up costing you $125 per month for ten years.  A pretty good buy.

Now the question becomes how much you are paying to heat and cool your home and how much would a geothermal system save you.  Assume that this system will save you between one-half and two-thirds of your current heating and cooling costs.  Even if you assume that it only saves you one-half, based on the above scenario, a geothermal system would be worth it to install as long as you pay on average more than $250 per month or $3000 per year.  If you pay significantly less than that, it probably isn’t worth it based purely on energy costs over 10 years.  However, note that your system will last for 30 to 50 years: so you will keep getting low cost heating and cooling long after you have paid for the system….and we have not factored in the price premium you get when you sell your house, let alone the value of the bragging rights for owning a very cool system.

Now let me answer your question a second way: geothermal will make the most financial sense for you, assuming that you have first done all the other energy efficiency tasks that have a higher return on investments.  Generally, these tasks would include things like air sealing and insulation.  It would NOT include things like new windows or solar panels–for the vast majority of people geothermal makes a lot more financial sense then windows or solar panels. So how do you know what to do to your home?  Start with an energy audit to prioritize all of these choices.

Harold Simansky


How to Find a Qualified Home Energy Assessor


Dear Andy,

I live in North Adams, MA and I want to get good advice about how to make my home more energy efficient.  I want to start with an energy assessment. I’ve read your post about the different types available. How do I find a qualified and trustworthy provider of a home performance audit?

Amanda K., North Adams, MA

Expert Answer:

Dear Amanda,

Think local! Local expertise matters more than you might think:

  • Typical home designs and materials vary from neighborhood to neighborhood: you want someone to perform your assessment who has good familiarity with the problems and opportunities that your home presents
  • If you need help with energy efficiency projects after the assessment, a local assessor will have connections with qualified local specialists
  • And of course local providers live and die by how well they serve their community – and since their travel time to get to you will be less, they have more time to understand your needs and figure out solutions that work.


For more info, check out our learn page on Home Energy Audits

Insulation Mold


Dear 360Chestnut,

Do you have any problems with mold when you damp spray cellulose?
-Teresa from Boulder, CO


Expert Answer:

Dear Teresa,
You can.  In fact, this has been the knock against damp spray cellulose for a long time.  As my friend, Tony Trigler at Anderson Insulation notes, “Back in the early 80s when there were a lot of wet spray cellulose jobs  spec’d out by the state of Mass, there were many problems – mold and sills rotting were common.”  Tony would know.  Anderson Insulation is one of the largest insulation companies in the country and has been around for more than 60 years.
However, now the world has changed a lot, insulators no longer “wet” spray cellulose, rather they “damp” spray cellulose meaning there is a lot less moisture to begin with, so for this new generation of damp sprayed cellulose, mold is very rarely an issue.
That said, there are certainly some best practices to follow when installing damp spray cellulose.  First, is go with an experienced contractor who has done this before.  Second, make sure you leave your walls open (no drywall) until the cellulose has properly dried.  Finally, you can only damp spray cellulose into  open wall cavities where the studs are exposed.  NEVER PUMP CELLULOSE INTO CLOSED WALL CAVITIES.  If you were you almost certainly will have a moisture problem.  [For that application, you would use dense pack (i.e., dry cellulose).]
I happen to like damp spray cellulose.  It is cheaper and greener than foam. Of course, sometimes foam is the right choice.
For more information on how to make that choice, go to our insulation pages.


Is Geothermal Cost Efficient for a Big House?


Dear 360Chestnut,
Will a geothermal system be cost efficient in an 8000sqft home? Will the electricty bill be high?
Tony from Long Island, NY


Expert Answer:

Dear Tony,
Let me answer each question individually.  With regard to does a geo system make sense for an 8000 sqft home, the short answer is it depends on how much you are going to use it.  If that is your permanent home and you live there year round, then the answer is likely to be yes.  If it is a weekend home, only used part of the year, I don’t think you’d ever get your money back.  My guess is that a geo system for your home would be in the $100,000 range less a 30% tax credit.

Of course, a lot depends on what your fuel options are.  If you have access to natural gas, natural gas  will almost certainly be the most economical choice. Today, though who knows what the future holds.  If you are forced to use either oil or even worse Propane, I would look for practically any other option.

So what would that option be?  Worth considering is a mini-split, ductless system, particularly if you are only using the house sporadically or only using small portions of the house at any one time.  The beauty of a mini-split system is it only goes on when you want it, where you want it.  It is highly efficient.

With regard to will you have a large electricity bill.  If you or your contractor mis-sizes the system you will have a large electricity bill because you will be using electricity as a back-up heat source.  It is really important that you have the system be properly engineered.  I would consider having a separate HVAC engineer size the system and then tell the contractor how big you want the system. Also, you want to consider having a non-electric back-up system for heating.

Your question begs another question from me, have you considered installing solar photovoltaic?  Solar PV would help offset your electric bill and then while you are not using much electricity or away it could actually sell power back to the grid.

Finally, it is my understanding that Long Island has a special electric rate for homes with geothermal systems: this is worth checking out.

For a next-step, I would suggest calling in a couple of geothermal contractors to see what they say.  If you need a connection to any, we have service providers in our network.

Let me know how it goes,



Do Solar Flares Effect Solar Panels?


Dear 360Chestnut,

I’ve been wondering…Do solar flares have any negative or positive effects on solar panels?




Expert Answer:


The short answer is no, solar flares will have no effect on solar panels.

The longer answer is not that much different.  Here is what we do know: a solar storm can reduce solar panel performance on a satellite that is orbiting earth by 3% to 5% in a day.  Given that such solar storms are very rare and that satellites are way out in space, closer to the sun, the effect of a solar flare on a terrestrial panel (like on your roof) is between, none and tiny.  The danger of the panel being damaged by wind, rain, snow, a tree branch, an errant ball is far greater than the danger of solar flares.

I hope this helps,


Solar Power for an Arizona Home?


Dear Bruce,

I’m thinking about solar panels for electricity.  What are your thoughts on this?  My house was built in 1956, a ranch-style house that’s common in my area.  Obviously, there’s lots of sun here.  Would solar be a good energy efficiency investment for me?

Paula G., Scottsdale, AZ


Expert Answer:

Dear Paula:

Well, you’re right about the resource overhead:  It’s estimated that your whole state could be powered by a solar array about half the size of Lake Powell, and that an array about 100 miles square could take care of the entire country’s electrical needs.  So why not grab a bit of that energy for your own home?  With photovoltaic (PV) panels more efficient and less expensive than ever, and with government rebates still in effect, now is a good time.

Your home sounds like a good spot for PV panels—as long as it’s not one of those rare Arizona houses in the shade of a huge tree.  No matter what part of the country you’re in, most solar-power companies will make a quick (and free) assessment to determine if it makes financial sense to put up a rooftop array.

However, before you start making calls—have you had an energy audit to determine how efficient your house is.  Is it insulated properly, is your HVAC system working efficiently, have you switched most or all of your lighting to CFLs?

In general, it makes sense to approach something like solar power only after you’ve lowered your energy consumption with adequate insulation, energy efficient appliances, and so on, which are much less expensive than a solar installation and can lower your bills dramatically.  In Arizona, you can get a basic energy audit for free, with more comprehensive assessments running a couple of hundred dollars.

Assuming your place is a good candidate for solar, you have a couple of options:  buy or lease.  If you buy, you own the equipment and can get a rebate on your purchase price. I looked up the details on the awesome DSIRE website (it stands for Database of State Incentives for Renewables & Efficiency)  and see that you can get a Federal tax credit worth 30% of your costs, with no maximum, and up to $1,000 state tax credit.  It also tells me that Scottsdale has a Green Building Program that provides expedited building plan review and a ton of information about local resources to help you to get solar on your roof.

But even with the rebates, some folks find the up-front costs—which average about $30,000 before rebates—just too much.  Leasing equipment means that you are basically loaning your roof space to a company that installs and maintains the equipment for free and provides you the electricity at or below market rates.  If you are ready to get started, you can Connect with a Solar Contractor on this site to be matched with a qualified contractor in your area.

Luckily for you, Arizona is one of 43 states that has mandated “net-metering” for its power companies.  That means you can sell whatever power you generate back to your utility, whether you lease or buy.  The new Holy Grail is “net-zero,” whereby your house produces as much power, averaged out over the year, as it uses.  May you find it!


Should I Go Geothermal?


Dear Chestnuts,

I live in Southeastern PA. My home is a 2 story colonial with full attic and full basement – approximately 2800 square feet of heated space. The house is nearly 33 years old and I expect to replace my oil burner in the next 5 years. My central heating system is hot water baseboard. Am I correct that a geothermal conversion will only make sense if I replace the baseboard loop with a hot air distribution system ?

Richard S.,  Rehrersburg, PA


Expert Answer:

Dear Richard,

The answer is…yes and no.  You can do a geothermal system with just a baseboard loop and you do not need to go to a forced air system.  The only problem is that under those conditions, the numbers may not work.  By only heating with your geothermal system and not cooling with it, you are using only half its capacity.  These “imbalanced” systems generally will not pay for themselves for years and years.  Without knowing anything about your own situation, I would anticipate a payback in the 20-year range.

I see you having three options:
1.      Damn the torpedoes, full steam ahead.  Maybe you are putting in the geothermal system for the environmental impact rather than return on investment.
2.     Move to a forced air system, which is the perfect fit for geothermal.  This way you also get air conditioning which you may want.  Of course, you will need to re-duct your whole house, which may or may not be a big job.
3.     If you are just going to make heat, you should look at converting to a high efficiency gas system.  If you can’t get gas, than a high efficiency oil system.  Payback on both is likely to be better.


Should My House Go Solar?


Hi Chestnuts,

One of my friends just put solar electric panels on his roof. It cost him about $30,000 (after rebates and tax credits) and now he says he only pays the minimum monthly meter charge
on his bill. We have a reasonably efficient (90% CFLs) 1986 home with an old
gas furnace that works fine, but no A/C is needed (since we replaced
West-facing windows and installed a whole-house fan). I’m considering solar
too but I’m having a hard time justifying that kind of expense when my power
bill is only ~$500/yr ($1000 including gas). What should I do?

Tom C., Sonoma, CA


Expert Answer:

Dear Tom:

Thanks for the great question!

We like the way you are thinking and progressing. The right approach is first to invest in all the sensible non-mechanical efficiency interventions you can to reduce your energy usage to a minimum and only then consider the eventual reinvention of your HVAC and electric systems – incorporating renewables wherever possible.

Without more data, we can’t necessarily be sure what your exact next steps should be, but here are some ideas to consider:

  • Have you done everything smart to reduce your monthly electricity usage? You already have CFL bulbs almost everywhere, but have you installed smart strips? Optimized appliances? Cracked the behavioral code for everyone who lives in the home? We know plenty of people who live normal lives in regular homes with electricity bills less than $40 per month.  The first step we like people to take is to unplug literally everything in your home, then only plug items back in on as needed basis (refrigerator first, obviously).  It is amazing what never gets plugged in again.
  • $30,000 net of rebates sounds a little rich for your property for solar PV; but even if the actual cost for you were $5000 or $10000 less, the economics of simple avoided electricity charges clearly do not add up.  On the other hand, solar is becoming almost an expected amenity on homes in your area of the state, so you also have to consider the likely positive impact of a solar PV system on your home’s resale value. So don’t give up on solar PV as an option at some point, particularly as technology advances and cost continue to come down.
  • And if the economics of solar PV do not make immediate sense, you could consider solar hot water as an option: a more modest investment and equally or even relatively more generous rebates in your area than for solar PV; right now there is a rebate of up to $1875 for a solar hot water installation in CA. Even so the economics will probably still not be compelling unless you see some upside on home resale value, but that is not such a stretch.
  • Of course for both solar PV and hot water, it’s important to note that non-economic environmental and political benefits are not insignificant and for some are entirely compelling. Reducing dependence on fossil fuels is generally good for the environment and for US geo-political security. For many there is a substantial dividend in knowing that all or part of their energy is coming from sustainable sources – and that they are minimizing their emissions, their responsibility for fossil-fuel related environmental disasters (such as the Yellowstone River most recently) or for keeping middle east oil autocrats in power.
  • This leads into the bigger discussion of “planning for the reinvention” of your overall heating and cooling systems. You mention that your gas boiler is “aging”, so it makes sense to be planning now for the right next move for your home. Many people wait until the system breaks down inconveniently – usually of course in the coldest spell of the year, when you have a house full of people home for the holidays.
  • We now make the assumption that you are not planning to move out of your home in the immediate future – in which case there is considerable appeal to creating a heating and cooling system which is as resilient as possible in dealing with the next 30 years of uncertain fuel prices (and even availability) and the potential impacts of climate change. In this scenario there is a strong case for incorporating renewable energy sources extensively in your plan. In fact, any reasonable assumption of incremental resale value is likely to make this the most economically smart option on top of the environmental and other benefits!
  • For instance, geothermal heating and cooling may be an option for your home: this is where you dig down deep enough to reach levels of the earth where the temperature is a constant level all year round, and you can use heat pumps to create heat for your home in winter and extract heat from your home in summer. If you have enough space to build such a system, you could eliminate your gas heating charges – with a modest additional electricity load to run the system – and that won’t be a problem with that solar PV system humming away.


Stuck with an Oil Burner


Dear 360Chestnut,
We installed a top-of-the-line hi-tech oil burner system about 7 yrs ago (w/hindsight and changing prices a mistake). We also installed full size gas pipe access, initially for cooking, but with longer view to possible heating w/gas. Is there any sensible configuration of installing a gas unit, while leaving the oil unit in place with alternate access to both?
Roger, Brookline, NH


Expert Answer:

Hi Roger,
I think you have a few of options:

1.       Retrofit your existing oil burner to burn gas (putting on a “gas gun”).  You are going to be knocking your efficiency down some but it should save you some money.

2.      Throw out your oil burner and go to a high efficiency gas burner.  While not a cheap endeavor it will have a great payback.  This is particularly true if your state offers any loan program or rebates.  Right now some states are giving between $1-2000 for converting from oil to gas and then interest-free financing to pay the cost.  Even with only a small rebate, I would expect your payback to be between 3-5 years.  You could even be cashflow positive immediately with the monthly payment on the loan to convert plus the cost of the gas actually being less than your monthly cost of oil.  Plus, you can get rid of your oil tank and claim back a piece of your basement.
3.       You could try to create some sort of combined system that maybe uses the oil furnace to do your heat but then you could use gas for a nice on-demand hot water tank but it is hard me to believe that financially that would make sense.
4.       Consider geothermal.  Geothermal is a great technology that will both heat and cool your home for pennies.  This makes the most sense if you already have a forced air system that both heats and cools.  Plus, the government now offers a 30% tax credit for geothermal, making it far more affordable then it has ever been.  Your state may even have rebates and loan programs on top of it.


Choosing the Right Heating and Cooling Systems for My Home


Dear Harold,

I have a 20 year old central air conditioning system. What are the economics of replacing it and do I need to replace the entire system because of the new coolants or can I just replace the condenser units My water heater will die in the next year or two, what kind of a system should I replace it with. I need new thermostats – how do I choose? Would I benefit from solar panels?

Chuck, Greater Boston Area


Expert Answer:

Dear Chuck,

With regard to the economics, without seeing any numbers it is likely to make sense to swap things out.  The devices you’re talking about replacing for higher efficiency units have payback roughly 3-8 years.  But this can change dramatically based on rebates and tax credits.  Also, if you can access the Heat Loan program (interest free loan, up to $25,000, payback over 7 years) it becomes a no brainer.

To access many of these rebates you need to do a free MassSave* energy audit.  You can also schedule an audit at  You won’t necessarily learn a lot but you will get a lot of free stuff and the rebates and heat loan are valuable.

One free thing you may get is 1-2 programmable thermostats.  With regard to thermostats you just want to choose one that you will use and it will work properly with your equipment.  MassSave* thermostats should be fine; there is the new NEST thermostat which is cool and easy to use.  Or if you upgrade your heating and cooling system, that will come with thermostats.

To get to the meat of your questions, first let’s define some terms:  your HVAC system is made up of a few different parts:

-How your heat is made
-How your cooling is made
-How your hot water is made


-How heating and cooling is distributed

I am guessing your heating and cooling is distributed by some combination of radiators and duct work.  Generally, these do not have to be changed or replaced assuming that there is no damage to them or they aren’t reaching particular rooms.

This being the case, with regard to your air conditioning system, you probably don’t have to replace the duct work but likely should replace the condensers.  Condensers are rated by Seasonal Energy Efficiency Rating (SEER).  Right now there is a tax credit for ratings of a SEER > 16.  I would be surprised if your current system had a SEER rating of 8.  You can also use the heat loan to replace the condensers.  To do this is in the neighborhood of $10,000.

With regard to your hot water tank, you have a few options: you can replace it with a standard hot water heater (ideally gas) and it is good for 10-12 years but is pretty inefficient.  You could be more sophisticated and get an on-demand hot water tank that only makes hot water as you use it.  These are great for homes that have less people, don’t need a huge amount of hot water, or folks who have more than one home, so aren’t at home for extended periods of time.  But if this is not you, on-demand won’t work great.

Finally, you could tie your hot water tank into your heating system for great efficiency but this should only be done as part of a system re-engineering.  Which may be appropriate depending on how old and efficient you boiler is.

With regard to solar, I believe you have a slate roof, so the answer is generally no.  You don’t want to do anything that could damage the slates, so I would forget about solar.  There are various systems that would allow you to put solar on a slate roof but I am skeptical, though I could be wrong.

So what to do?  The rough and ready solution is swap out your condensers and hot water tank, and get some free thermostats, all for about $15,000 (very rough figure).  Or re-engineer your system, moving toward something like an integrated hot water tank, maybe geothermal.  This could be over $50,000 but between the tax credits and the Heat Loan, your out of pocket cost could be a fraction of that with a great payback and ROI.

So how do you know what to do to your home?  Start with an energy audit to prioritize all of these choices.

Harold Simansky

*Disclaimer: 360Chestnut/BTW is not affiliated with MassSave or The RCS Network.


How to Insulate Basement Wall next to a Water Heater


Dear 360Chestnut,

I have a wall in my basement that is maybe an inch away from the water
heater itself. I was going to use a standard R-13 fiber glass
insulation. Will that be alright?

-Donna, Brookline, MA


Expert Answer:

Dear Donna,

The short answer is that it would alright though I think there are better solutions.

First air seal, air seal, air seal.  I would grab a can of caulk and
just fill every hole and crack you can find.
If your thought is to leave the wall intact, not open up to the studs, and just slide some insulation between the wall and hot water tank you will have better luck using a rigid foam board like an extruded polystyrene rigid insulation (also known as Styrofoam) with a foil back.  That would bump you up to about R-5 per inch.  This is a cheap easy solution.  Of course, only after air sealing.

If you are opening up to the studs, fiberglass is fine, as long as you air seal. Better is using a foam insulation which you can do yourself.  Foam air seals and insulates.  Easy but more expensive.

If you send a picture of the application and tell us if you are
opening to the studs, we can be more specific.

Thank you,



Why isn't geothermal energy more mainstream?


Dear Chestnuts,

Geothermal energy seems like a great option for heating and cooling, especially for new construction.  Why isn’t it more widely used?  Are there special considerations when it comes to geothermal energy?

Nancy T., Baltimore, MD


Expert Answer:

Hi Nancy,

The other day, I had the opportunity to be a guest on Heatspring TV with Chris Williams.  Chris and I just batted around our thoughts about geothermal energy, why it’s not more mainstream, and how we get the word out. You can see it here.


For those of you who aren’t familiar with Heatspring TV and the Heatspring Learning Institute, Heatspring is an education company focused on providing clean energy training to building professionals.  At this point, some 3,000 professionals across the United States have learned about Geothermal and Solar Electric systems through the courses Heatspring offers.


What my conversation with Chris reminded me was just how important the engineering of the geothermal energy system itself is.  A system that is too small or too big can cause a lot of problems, not the least of which is a system that is really expensive to run.


Engineering a correctly-sized system is not a trivial thing but even non-engineers can do it assuming they have the background.  Of course, the question then becomes how do you know that your contractor knows how to size a system correctly?  The answer: call a lot of his customers and ask them during the winter how much do they have to use their supplementary heating system. They would know this if they have a big electric (assuming an electric back-up system) or a large gas bill (assuming a gas back-up system).  If they have big bills during the winter, the system has been mis-sized which is a reason for you to look for another contractor.


We agree with you that geothermal energy makes a lot of sense.  As more contractors become familiar with its potential for residential housing, we think this new technology will really take off.

Will an Energy Efficient House Be Worth More?


Dear Becki,


Hi, I was wondering if any studies have come out showing value appraisals of standard buildings versus comparable green buildings.

Michael S., Chapel Hill, NC


Expert Answer

Dear Michael,

Any property appraisals comparing an energy efficient building to a standard building wouldn’t yet yield any definitive answers on whether one building is worth more money than other. What’s more, it’s difficult to pin down at exactly what point a building can be defined as “green”.  Depending on how sustainable you want your building to be, it could raise the upfront costs anywhere from 2%-30%.

You’re going to pay more for energy efficiency, at least for now.  The materials and installation techniques are relatively new and therefore increase the cost–although there are many rebates and incentives that will bring down the price. 

Proponents of sustainable building often scoff at these “upfront” costs of the project, looking instead at the cost savings over the lifetime of the building—known as “lifecycle” costs.  I think this is a mistake.  Developers and homeowners are naturally concerned with upfront costs.   But, when you reduce the idea of sustainability to its essence, which is energy efficiency, the things that you do to make your building “green” are the same things that any person should do to add value to their property.  Tightening up the building envelope, especially in new construction, by putting in energy-efficient windows, or adding insulation with a higher R value than is required by code can go a long way in reducing the energy needed to heat and cool the building and would prove to be good financial investments both long and short term. It might not be as sexy as putting $20,000 worth of solar panels on your roof or bamboo flooring throughout your building, but reducing energy consumption is where the sustainable market should be focusing its attention.

A 2003 report by the California Building Task Force shows a scientific break down of sustainable buildings, comparing upfront cost to lifecycle costs.  It’s a little dense, but it might give you more information on the costs and savings in green design.

When it comes to the question of whether or not home-buyers are willing to pay a premium for a “green” house, the evidence is mounting that the answer is yes. Around the country, sales of eco-friendly homes represent the one bright spot in an otherwise lagging real estate industry, and many builders are finding that it’s their clients who are asking them to add sustainable features and functionality.  Still, the appraisal community is lagging behind, sometimes even requiring homebuilders to eliminate energy efficiency projects, so they can more easily compare properties.  It will take some time for bankers, underwriters, and appraisers to understand the long-term value of energy efficient homes, unfortunately.


What does properly blown insulation mean?


Dear 360Chestnut Expert,

What does PROPERLY blown in insulation mean? What would be an example of NOT properly blown in? Also, I thought that newsprint contains formaldehyde to prevent it from mildewing.

-Donna, New Jersey


Expert Answer:

Hi Donna,

Excellent questions.  First the easy one: fiberglass has formaldehyde, cellulose does not.

With regard to what PROPERLY blown insulation means, it depends on the application.  In an attic, properly blown means equal depth in every piece of the attack, particularly the corners.  In walls or when you dense pack, it means that the cellulose has been installed using the correct amount of pressure to insure it compacts fully.  Properly installed dense pack cellulose weighs between 3.5 – 4 lbs per cubic foot and is generally blown at a pressure of 80-100 psi.  There are tools to measure this.  After the fact, a thermal scan can reveal any gaps that may exist.

Here is a video we did about cellulose that you may find interesting.



What are the Different Types of Energy Audit?


Dear Andy,

Can you tell me about different types of energy audits and how I can determine which one is right for me?

Brenda L., Akron, OH

Expert Answer

Dear Brenda, Yes, there is a wide spectrum of services, which are called “energy audits” or “energy assessments” – and they vary tremendously in cost and value added. Here is a summary of 4 major categories of home audit and our recommendations for which ones make the most sense for the average homeowner:


1. FREE Manufacturer Audits The cheaper the audit, the more likely it is that the auditor has fewer qualifications and that he or she is really doing the audit to get a foot in the door in order to sell you on a particular product or service. For instance, some window manufacturers offer “audits” to tell you “how much money you could save” by installing a lot of new windows; sometimes their “auditors” use thermal cameras to show you cold air moving in an around your existing windows. However, this is a sales pitch, not an energy audit!
2. Subsidized Utility Audits: free or low cost if you follow up on recommendations Be sure to see what’s available through your local utilities: many offer free or reduced rates: and these are often of reasonable quality and may also qualify you to access generous rebates for energy saving measures.  However, be aware that some utility auditors are not allowed to discuss all the issues that should be part of a comprehensive audit: in particular many utility subsidized audits do not cover your options for switching heating fuels – which is frequently a highly significant issue!
3. Comprehensive Home Performance Audits: $400 – $750 For a comprehensive audit, reach out to a local qualified home performance contractor –  who will come to your home for 2 to 4 hours and develop a complete evaluation covering:
–The leakiness of your building
–The quality of your insulation and windows

–The safety of all your heating, cooling and cooking equipment
–The efficiency of your heating and cooling equipment and opportunities for improvements
–Electricity consumption patterns and opportunities for savings
The auditor we recommend will use a combination of tools to scientifically measure the performance of your home and diagnose issues:
The blower door test:  identifies how leaky your home is and can help to isolate where the leaks are
The thermal camera:  when there is a sufficient temperature differential between inside and outside, this camera can literally look into walls and windows and identify where hot or cold air is escaping or infiltrating
The combustion analyzer:  makes sure that any gas-fueled appliances or heating equipment is running safely.

However, the most important step is the time the auditor spends with you understanding what your particular concerns and constraints are – and then explaining the findings and recommendations. You should expect a menu of steps – large and small – which you can take over time to achieve substantial savings, with a ranking according from quickest to slowest payback.

4. Professional Home Energy Modeling: $1000 to $2000 At the more sophisticated end of audits are detailed examinations by specialists trained in the “Home Energy Rating System” (HERS). These specialists develop a detailed model of your home’s energy performance starting with the construction and insulation characteristics of every element of your home’s construction. With this platform, HERS raters will advise on the most cost effective steps to improve the energy efficiency of your home and can model the efficiency improvements. Not recommended for the average homeowner, this level of detail will be attractive if you are committed to pursuing a deep energy retrofit for your home.
Behind the Walls
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