Spray Foam vs. Fiberglass - R-value only?

While fully wanting to have the most thermal barrier I can have, should I believe Rem/Rate when it tells me that R-value does so little? By changing the R-value # only for the ceiling (roof) in Rem/Rate, the cost savings is ~$75/yr on my house specifically, and the load reduction and carbon reduction are also nominal.

There is the ongoing discussion about cheating the customers by only spraying R-21 in lieu of R-30 (our local R-value requirement). The diminishing returns after a complete air seal is met with spray foam seems to suggest there is no need for the extra costs. I don't think it is debatable whether or not the greater R-value # you have (thickness), the more thermal resistance you should have if it is installed properly. But should the insulation types be counted as equals? Should we make it so tough to put the ducts in the envelope?

As I understand it, R-value for code has been based on conductance only and not the 2 other types of transfer. By not giving spray foam credit for the air sealing qualities it potentially has seems to make the two types an unfair comparison.

The only thing I think must happen is the enforcement of code regarding air leakage testing of all spray foamed and air sealed houses with blower doors, new and retrofit. With all the homes that I have been testing, there is obviously a need for this service. So many of these installers have been looking at this like painting and not using building science in their approach. There are huge energy saving claims by many of these companies, and the housing stock and clients are not getting a good deal.

Those building envelope gaps are a plenty!! This past summer in the hot/humid environment of Hilton Head Island, SC, those newly spray foamed attics were hot/humid, and those ducts were dripping condensation like crazy! Small mistakes in spray foam seems to be the cause of lots of problems.

One big question that also needs to be addressed is, how do you know if the house is too tight and you need ventilation without testing? Not many around here are testing. Some of these retrofits have gas appliances and are in retirement communities. I see potential concerns for health and safety here.

Of course there is the article titled "It's OK to Skimp On Insulation, Icynene Says" by Green Building Advisor contributor Martin Holladay which clearly states his position. Although I agree that requirements are requirements and codes are codes, what should we do about the ROI and the information our energy modeling software tells us? If we make it too hard and don't give constructive guidance, how are we going to move forward?

What are some thoughts on this?

Tags: Blower door, Building Envelope, R-value, fiberglass insulation, spray foam insulation

▶ Reply to This

Replies to This Discussion

Permalink Reply by Adam Zielinski on December 6, 2010 at 11:01am

I have seen good results wih the flash and batt approach under floors in crawls. Spray 1-2" of closed cell foam and then fill the rest of the cavity with batts to get whatever R value you need. You can even cover the batts with Tyvek on the cold side to provide more of an additional air barrier.

The main problem with open cell foam is that it will absorb moisture and can become soaking wet like a sponge. It's just not much of a vapor barrier. I can't imagine that being good. I have heard people talk about horror stories with spray foam on wood in climates like Alaska, but not in the lower 48.

The BPI mechanical ventilation standard is a 21 year old ASHRAE standard and is obsolete and outdated. If you go by the current ASHRAE standard 62.2 - 2010, you won't have any problems with moisture or stuffiness. Just always install a HRV when you spray foam a house up tight.

Gas stoves are fine but always need a range hood vented to outside, and homeowners need to use them when cooking. Move all natural drafting combustion appliances outside or upgrade them to sealed combustion/direct venting.

▶ Reply

Permalink Reply by Al Heath on December 6, 2010 at 12:47pm

Maybe you should try a modern electric stove big difference from the old ones, I used to prefer gas too. CO exposure at any level is under investigation for its possible connection to asthma and Alzhimers (sp?) As to gas being more efficient? Electricity is a potentially renewable resource, most gas is from fossil fuel origins and therefore is not.

▶ Reply

Permalink Reply by allen p tanner on December 6, 2010 at 5:36pm

I have open up walls and crawl space areas that were sprayed some years go, (5, 10 and 12). You would not believe how much the insulation shrunk, became power or just fell out. Wait 10 or so more years out. Will all these homes have major mold/air leakage/ other issues?

▶ Reply

Permalink Reply by Jamie Kaye on December 6, 2010 at 5:49pm

Something is wrong with that insulation Allen. The old PolyUrea foam did have some problems, but the new foam will not shrink or turn to powder. I don't think that is what we should be worrying about regarding the foam. I think the lack of experienced building science people installing it is what should be of concern. They are missing so many bypasses and are potentially creating a worse situation. That mixed with the fact that none are really testing to see if they need ventilation or doing CAZ tests. Those are my concerns, but besides those, I love the product!

▶ Reply

Permalink Reply by allen p tanner on December 6, 2010 at 5:57pm

How many Infrared inspections are taken of the spray foamed areas the next winter, 2 years later to see how much the material has shrunk or degraded?
IThat is definatley the technology to follow the spray foam up with.

▶ Reply

Permalink Reply by Jamie Kaye on December 6, 2010 at 7:21pm

Allen, I have seen foam that was not mixed properly become crumbly. (A) side/ iso heavy. The mix is the magic here and getting and maintaining a good yield and mix is very important. The temperature of the material that the foam is being applied to is important as well. If it is too cold, it may not adhere well. In rafter bays, you can push on the foam and it will flex (bounce) in the middle if this has happened. This could be a potential problem.

I do use thermal imaging, but I have also been in houses with older foam and have not noticed a difference or the same effects. I did see pictures of the older polyurea foam in my thermal imaging course where it showed what looked like cracks in the foam. Maybe someone here has some pictures and better info here.

▶ Reply

Permalink Reply by Evan Mills on February 28, 2011 at 5:43pm

Folks might want to comment on this new Forum post with concerns about the quality of application of spray foam in enclosed wall cavities.

http://homeenergypros.lbl.gov/forum/topics/rebate-programs-for-inje...

▶ Reply

Permalink Reply by Robert H on March 1, 2011 at 9:28am

Spray foam would not cause condensation - actually sorption on the bottom of the floor above a crawl space. For starters the crawl space should be vented if the floor is sealed. The bottom of the floor will be above the dew point as it would be protected by insulation. Further we dont need condensation to have moisture problems. RH above 60% is going to allow mold to grow. I would suspect that the RH would stay below 60%.. If open cell were used it would need some sort of flame spread barrier and I assume these would act as a vapor retarder.

▶ Reply

Permalink Reply by Tom Mallard on March 1, 2011 at 2:38pm

Foams trap moisture so I'm reluctant to use them at all, moisture transport must be considered here in Seattle or the place becomes a fungal palace, foams causing dry-rot fairly consistantly.

The essential thing to remember is heat-transfer is directional, adding more insulation won't do much once it gets to a certain point because nothing in the system is storing the heat-cold, it's a one-way street.

Some adobe homes stay cool all summer w/o air-conditioning, with insulation in the system you don't need as much thermal-mass, heat-sink, same-same, it's a mass large enough to regulate the comfort-zone in the room pretty much with 10% of the thermal inputs for the same room without it.

So in a ceiling system my solution is more sheetrock once that insulation point has been reached, walls or ceiling, 5/8" heavy stuff. I can't check this with software so ymmv, but it works, basically what it does is add more time between inputs, keeping the added mass to the room side of the insulation.

I have other fancier ways using thermal-fluids to move the heat from there to the floor again but those are not product lines yet so not available.

hth, tom

▶ Reply

Permalink Reply by Bryce Cramer on March 2, 2011 at 6:53am

I'm a firm believer quality of installation is key to the effectiveness of any insulation. To say that one is better than another is not being fair to those that do a quality job of installing and giving credit to those that do poor jobs.

I've found foam good for some applications, while cellulose is better for some. Wouldn't it be nice if one size fit all? Unfortunately, we all know that's not the case.

Here are some photos of a new home that was built with spay applied foam, very high energy consumption. Can you figure why?

▶ Reply

Permalink Reply by allen p tanner on March 2, 2011 at 7:34am

This doesn't look right for a 'new' home. Where was the site superintendant while the sub was working, did the sheet rockers just rock over missing insulation?

This does not appear to be shrinking. The foam installers should have used an IR camera while installing to confirm even heat and foaqm distribution.

Did you open the ceiling, gain attic access or probe for further information?

▶ Reply

Permalink Reply by Bryce Cramer on March 2, 2011 at 11:09am

They flat missed this area (was done after s-rock was installed), as well as a similar area in another bedroom. They also had a lot of "seam" issues.

▶ Reply

RSS

Welcome to
Home Energy Pros

Sign Up
or Sign In

Or sign in with:

Home Energy Pros

Home Energy Pros was founded by the developers of Home Energy Saver Pro (sponsored by the U.S. Department of Energy, under the American Recovery and Reinvestment Act) and brought to you in partnership with Home Energy magazine.