Is retrofit foam insulation worth it?

[zknowlto]

My wife and I had a wood burning insert installed last year, in part, to take advantage of the EPA tax credit. As the insert didn't end up costing $5000, we would like to do another project this year that lets us collect the rest of this credit. We live in a 1930's home, about 1600 sq/ft, with no wall and very little attic insulation. Today, I spoke to a local company that quoted me a price of $4500 to blow in attic insulation to R-38 and foam wall insulation (Air-krete) to R-20. With our remaining EPA credit, this project would come to a little over $4000.

The guy told me that I could expect 30-40% energy savings by insulating. Looking at my gas bills and calculating the cost of wood around 150/cord (though all I have now was scrounged), I figure I'd save around 250-300/year if this is true. My questions are:

1) Does $4500 seem reasonable for an installation like this?

2) I'm like 90% sure I want to go with foam for the walls (doesn't settle, fills in all the gaps), but is there any reason that I should reconsider cellulose?

3) Does the 30-40% figure sound right? I'm basing all my calculations on these being minimums. I wouldn't even consider a project like this if I was going to save, say, 5%.

4) I realize the rate of the return on this isn't great (12-16 years if I've done my math correctly), but I'm hoping that houses with improved insulation "feel" warmer. All other things being equal, are well insulated houses more comfortable?

My thanks in advance for your advice!

 

[btuser]

Cellulouse won't settle in the walls if its done right. 30-40% is not impossible, but remember that 50% goes through the attic, and you only lose about 10% through the walls when you seal openings/penetrations. Up to me I'd blow in the cellulose because it keeps out the mice! New construction is different.

Difference in price between cellulose in the walls? Big money? Done right its your best bet.

 

[benjamin]

personally, I like cellulose, but then I do it all myself and I'm not familiar with "air Krete". I do know some of the first generation pour in foams (decades ago) had a bad track record, they would shrink and settle, and ended up being far less effective than a bad cellulose job.

On the other hand, everyone I've heard recently who had done foam has loved it.

I would say 30-40% is slightly optimistic for just insulating the walls. Of course it depends on how well the house is sealed up already. If you have balloon framed walls with no blocking then it's easy to save 50%. Your numbers indicate that you spend under $1,000 a year for heat. If that's the case, there's no way you're going to save 40% just by insulating.

On the other hand, insulating a house with no insulation makes a huge difference, and even if the payback is 15 years, if it had been done 15 years ago you wouldn't be debating this now. The point is that unless the house is going to be torn down, it will be insulated at some point, so decide which way is best and do it.

If you go with cellulose, you also want to seal all cracks and penetrations from the inside into the attic before you make the mess, and maybe even before you blow foam, depending on how much you trust the foam.

 

[Slow1]

I can't answer the question on foam in the walls, but I can tell you that when we added a "mere" 4 inches of cellulose in the attic and sealed up around pipes etc up there, it made a huge difference in the comfort level. My wife (who generally is rather oblivious to these things) noticed the difference in a matter of days and has commented more than once since then that she felt that was money very well spent.

Now I can't say which did more - the cellulose or the air sealing up there, but the point is that attic work can make a major impact on things.

 

[GaryGary]

My wife and I had a wood burning insert installed last year, in part, to take advantage of the EPA tax credit. As the insert didn't end up costing $5000, we would like to do another project this year that lets us collect the rest of this credit. We live in a 1930's home, about 1600 sq/ft, with no wall and very little attic insulation. Today, I spoke to a local company that quoted me a price of $4500 to blow in attic insulation to R-38 and foam wall insulation (Air-krete) to R-20. With our remaining EPA credit, this project would come to a little over $4000.

The guy told me that I could expect 30-40% energy savings by insulating. Looking at my gas bills and calculating the cost of wood around 150/cord (though all I have now was scrounged), I figure I'd save around 250-300/year if this is true. My questions are:

1) Does $4500 seem reasonable for an installation like this?

2) I'm like 90% sure I want to go with foam for the walls (doesn't settle, fills in all the gaps), but is there any reason that I should reconsider cellulose?

3) Does the 30-40% figure sound right? I'm basing all my calculations on these being minimums. I wouldn't even consider a project like this if I was going to save, say, 5%.

4) I realize the rate of the return on this isn't great (12-16 years if I've done my math correctly), but I'm hoping that houses with improved insulation "feel" warmer. All other things being equal, are well insulated houses more comfortable?

My thanks in advance for your advice!

Hi,
You can estimate the savings yourself with this calculator:
http://www.builditsolar.com/References/Calculators/InsulUpgrd/InsulUpgrade.htm

You will need to estimate the before and after R values for walls and ceiling -- there are some help files to help you do this.

I'd maybe get separate estimates on ceiling and walls and evaluate each separatly -- blowing more insulation in the ceiling is pretty much a no-brainer. If the walls don't currently have any insulation, that should pay well also even though its more expensive.

I'd join the others in saying I like cellulose for both the walls and ceiling. If the cellulose is dense packed it will never settle, and its also a pretty good air infiltration barrier. If the installer does not know what you mean by dense pack, then I'd get another installer.

Most of the places list the R value of Aircrete as "similar to fiberglass" -- this makes it about the same or a bit worse than dense pack cellulose.


Its really important to seal all the ceiling penetrations BEFORE blowing in more insulation. Every pipe, wire, light fixture, vent fan, ... Flow from living space into attic with a matching cold air inflow somewhere else is a major part of infiltration heat loss.

If you have heating ducts going through the attic, you want to seal all the joints with duct mastic, and insulate any ducts that are not insulated. Duct losses can be very large: http://oikos.com/esb/28/duct_losses.html

Not to be a cheerleader for my site, but you might want to check the "Conservation" page and the "Half Plan" page to see if you have really picked the best payoff ideas for your remaining credit www.BuildItSolar.com -- usually its hard to go wrong with adding insulation, but always good to check.

Gary

 

[DBoon]

I have a 1250 square foot home in Central NY that was essentially uninsulated (no wall insulation, only R-19 in the attic, no floor insulation). It used nearly 1000 gallons of heating oil in an average winter when I bought it.

I added another 8" of fiberglass to the attic (R-45 total) and sealed up the hatch really well.
I added 6" to the floors (R-19).
I had the above-grade basement foundation walls insulated with 2" of foam.
I had the walls insulated with blown-in fiberglass (R-16).

Now, my house would use about 550 gallons of oil in an average winter (if I wasn't using my wood stove). This is about a 45% reduction in use of heating oil. My hot water is electric, so the reduction is due totally to the insulation.

Even if you heat with wood, I would say spend the money and get this done if you can afford it. It will mean less work for you with the wood stove, less wood handling, more comfort overnight, less drafts and more comfort overall with more even heat throughout the house.

 

[BucksCoBernie]

Today, I spoke to a local company that quoted me a price of $4500 to blow in attic insulation to R-38 and foam wall insulation (Air-krete) to R-20.

I did cellulose in the attic this past January and it made a big difference...I had zero insulation up there. I did it myself for $600. If you buy X number of bags from HD you get a free days rental of the blower machine. It was pretty easy to do. I had a friend feed the machine and I blew the product into the floor joist.

I want to get some foam installed in my addition walls...there's zero insulation in there also....its brick, about 1.5" of space, then drywall. no wonder im freezing my butt off in winter back there. The onlything that would get a decent R value for me would be the foam since the gap isnt that deep...i might even re-stud and get a little deeper.

let me know how the foam in the walls works out for you.

 

[pyper]

Someone at some point in time had cellulose blown into the walls of our house. As we remodeled I took each wall down to the studs, and the cellulose had all settled. Some places more than others. Pretty much any wall cavity that had any exposure to outside moisture was more settled than the others. Not a fan of cellulose for that application. But I did blow some into the attic. Pretty easy and cheap to do that.

Forget about the cost savings. That's nice, but here's why you want to do it: it will make your house 100% more comfortable. The first winter we were in our house it was really cold. When we got first frost it would be freezing in the morning (no good source of heat either, but that's not this story). So that summer we installed R 3.8 rigid foam insulation on the underside of the floors. This small amount of insulation made a huge difference in comfort. The second winter that first frost came and went. It wasn't warm in the house, but it wasn't freezing cold, either.

So don't neglect your floors.

Remember: heat radiates uniformly in all directions, and the floor is pretty big.

 

[GaryGary]

Someone at some point in time had cellulose blown into the walls of our house. As we remodeled I took each wall down to the studs, and the cellulose had all settled. Some places more than others. Pretty much any wall cavity that had any exposure to outside moisture was more settled than the others. Not a fan of cellulose for that application. But I did blow some into the attic. Pretty easy and cheap to do that.

Forget about the cost savings. That's nice, but here's why you want to do it: it will make your house 100% more comfortable. The first winter we were in our house it was really cold. When we got first frost it would be freezing in the morning (no good source of heat either, but that's not this story). So that summer we installed R 3.8 rigid foam insulation on the underside of the floors. This small amount of insulation made a huge difference in comfort. The second winter that first frost came and went. It wasn't warm in the house, but it wasn't freezing cold, either.

So don't neglect your floors.

Remember: heat radiates uniformly in all directions, and the floor is pretty big.

Hi,
The cellulose won't settle if its installed right -- that is, if its dense packed.

Some collected info on blowing cellulose in walls:
http://www.builditsolar.com/Projects/Conservation/WallCellulose.htm

The Insulate and Weatherize book by Bruce Harley is a really good one for people who want to do their own insulating and air sealing. It covers the right way to install cellulose.

Like anything, there are installers who do it right and others that do it wrong.

The big advantage that cellulose has over fiberglass (I think) is that it does not allow air currents through the insulation. Fiberglass can lose as much as half its R value under cold conditions:
http://www.homeenergy.org/archive/hem.dis.anl.gov/eehem/92/920510.html
and
http://www.builditsolar.com/Projects/Conservation/Insulation/Colorado.pdf

Of course, if you are in a position to install closed cell foam, this will perform better than either FG or cellulose.



Gary

 

[fishingpol]

I had cellulose blown in my attic and a few walls in rooms that I did not remodel in my 1910's house. Best thing I did after putting in a stove. They put 8" in the attic and it does make a difference. The attic access hatch was 24" x 24" in a closet but I sheetrocked it when done since there is no storage up there. The insulation supervisor did a blower door test in which they put a fan and platic sheet frame in the front door and closed all the windows and doors to see what the air infiltration was. As I recall, they cut the air infiltration 50% when they were done. I actually watched the test and he showed me the results on the digital readout. They also did air sealing to every penetration, pipe, wire, plumbing stack in the basement. Before on a hot summer day, you could feel the heat through the south facing walls with your hand pressed against it. Now, no more, saves elec in a/c costs. They also did a combustion test on my hot water tank and boiler to make sure they did not seal the house to tight that it would effect drafting.

Make sure you have all old wiring replaced, especially knob and tube. I had to have an electrician sign off that it was all replaced. There was one nightmare circuit in the attic that I did not know was up there. It was 3 knob and tube circuits run off of a bx line, buried under a little insulation. :ahhh: Sometimes it is better to put the risk and liability on an insured contractor than do it yourself and have a p.o.'d insurance company if you miss something and things go south.

On a sidenote, I helped my neighbor gut a few rooms in his 1890's house. The prior owner had blown done at least 15 years ago. Looked like it was put in yesterday, no settling.

 

[tom in maine]

It is 2010, I cannot think of any reason to not invest in fully insulating a house.
It seems a little silly to handle any more wood or burn any more oil/gas than you would need to.
$4500 sounds a little dear for insulating an attic, IF it is a simple blown in installation.
There should be a MINUMUM of 14" up there. Many are going with 18+ inches since it is an easy place to lay it on thick.

If you insulate the attic and not do the walls, the heat loss of the walls is going to be over 50% of the house's load.
And the walls will become a place where condensation can take place. Please, always insulate walls.

You can DIY the attic. It is a fun experience to do once!
Seal all the penetrations into the attic, ie: vent pipes, wiring, etc. before blowing in the cellulose.
The access hatch should be weatherstripped and insulated.

The walls might be better left to a competent experienced person. Cellulose in walls should be installed to at least 2 pound per cubic foot
density. This is dense enough that when you poke your finger into it, you will meet with some resistance.

Price out the insulation at Home Depot or a local lumber yard to see if it is worth doing yourself.

I have done enough attics myself, that I am happy to pay someone to do it for me.

Air Krete is a decent wall insulation. I have not used it. One really good thing about it is that critters will not burrow through it.
If there is access into a wall cavity, mice will burrow in fiberglass and cellulose. It is warm and very comfy to them for nesting and homes.

 

[zknowlto]

Thanks for your comments everyone. After posting my original message, I ended out getting an estimate from another company for insulating the walls and attic with cellulose insulation. Their proposal was essentially identical to the company selling foam, very similar r-values and price. In the end, we decided to go with the foam insulation. While I fully accept that properly installed cellulose insulation is fine, I just felt like the foam had a number of advantages that justified it.

I'm glad we got this done, but I have to say that insulation seems about the least "sexy" home improvement you can have done, especially during the summer in a house where we barely every use the A/C. I'm really hoping this pays off in less fuel consumption/reduced heating cost/increased comfort this winter.

 

[btuser]

You're wrong about insulation. A warm house is the right kinda house for sweet luvin'!