Q&A Forums

closed cell in new house Post New Topic | Post Reply

Author Comments
Brian Langston
Posted: Aug 27, 2011 09:19 AM
closed cell in new house
I'm having a new house being buit - cape style, with a 3 car garage as part of the building.

My builder and I are having a 'disgreement' as to what is needed/wanted for the insulation.

I requested closed cell foam on all exterior walls and the roof deck, as well as 'encaspulating' the garage. So in other words, the entire building envelope.

Part of the envelope is the garage, and above the garage is about 600 sqft of an unfinished bonus room. I designed/planned it this way to make finishing it easier. since the floorboards will be insulated already (it's over the garage) and all the walls and roof deck are insulated, I can simply add electrical, hvac, and drywall and carpet.

The question comes from the wall separating the unfinished room and the living spaces that will be finished.

His first insulation contractor was a moron, and just asked what he wanted and didn't give a recommendation of anything.

Should not the conditioned spaces be insulated, or is it unnecessary, since the entire building is encapsulated? If that wall is not, shouldn't the HVAC contractor take that space into account for heat loads, or it will be insufficient?

There is also a section on the opposite side of the house that will become unacessible attic space - shouldn't all the walls be insulated that have conditioned space on the other side of them, or is just drywall enough?

I can post pics of the plans if it would make it easier to understand.

Thanks everyone, I've learned a ton from this site and just want to make sure my new house performs the way it should.
John Shockney
Posted: Aug 28, 2011 10:49 AM
Personally I would definitely insulate the wall to the inaccessible attic unless the attic is a “conditioned attic” that is, is the insulation applied to the roof or the floor of that attic? If the attic is conditioned then the wall would not need to be insulated.

As for the wall between the living space and the bonus room should not need to be insulated and will not add enough heat loss/gain to require up sizing HVAC equipment as long as the roof insulation package is in the R-35 to 40 range. Besides your HVAC contractor has almost certainly oversized the system for a spray foam insulated house.

Hope this helps

Airpro Heating and Air Conditioning
Airpro Spray Foam
Brian Langston
Posted: Aug 28, 2011 11:23 AM
Well, I am having a manual J done, so it should be sized properly.

The inaccessible attic portion will be insualated as the entire roof deck is insulated and the exterior walls as well.

R35/40 seems a bit overkill. Ive always read that R value is overrated regarding spray foam and after 3.5in the benefit is negligible. I plan on 2.5in on the walls and 3.5 on the roofdeck.

I dont mind not doing those walls if they are not needed, I just want to make sure the hvac doesnt need to count that as conditioned space since it wont have registers.

Also, Im in the southeast (SC) temps easily get to the 100s in the summer, and as low as the teens in some winters.

House has the front door facing south, garage is on the west side, and there is only one window on the east side.
Brian Langston
Posted: Sep 24, 2011 10:41 PM
So, the foam is done! It looks great! They did overkill in many areas, but it was spec'd at 2.5" on the walls and 3" on the roof deck.

The A/C has been spec'd as 2 units - a 1.5 ton and a 2 ton. Both has a 4in fresh air intake duct to them.

In my thinking, that sounds like I'm leaving 2 - 4in holes in the side of the house all the time. Isnt that killing the benefit of the foam?

Ive seen a honeywell damper recommended before - would that be the way to go with this? I cant afford to do an ERV/HRV right now, and didnt think it was necessary.

Any thoughts?
John Shockney
Posted: Sep 25, 2011 01:03 AM
The air intakes should have a barometric dampener installed in each that should only allow air to flow into the house to prevent the house being in negative pressure by providing makeup air when exhaust fans or a clothes dryer is running.

I still think that R-20 in the roof isn’t enough insulation even in the southeast unless your roof is white, but I may be wrong. Please let us know how your heating and cooling costs go we always like to get real world data back.

Brian Langston
Posted: Sep 25, 2011 01:06 AM
Thanks! Do you know if the honeywell damper would work? I think they are around $200 bucks each, and have controls as you mentioned.

I originally thought I'd go with 3.5" on the roof, but the insulation company said they typically only do 2" in the walls and 2.5" on the roof deck.

The foam they use has a aged R value of 7.4 per inch. I thought that was a bit higher than most, not that R value is a great measure.

I don't think I posted earlier, that it's a slab too. Not sure if that would make a difference in anything, other than not having any foam under floorboards on the first floor.

I was really hoping to go with some SEER 19 heat pumps, but I could only do 15s. :(
Posted: Sep 25, 2011 07:33 PM
Aged R- value of 7.4???? I'd like to see the ESR on that one. I'm always looking for a better foam. The best I've found is 6.9. What brand of foam is it? I agree with Airpro. We try to spray a 4" minimum on the roof deck. I think you will need an ERV also. Just my 2 cents
Brian Langston
Posted: Sep 25, 2011 08:36 PM
Thanks for the replies. I'm going to have to go sans the ERV for now and I'll add if the humidity stays too high.

Would a dehumidifier be an option as well? I've seen where ERVs are not recommended in hot humid climates, and Columbia, SC certainly qualifies as hot and humid.

The foam they used is Demilec HeatLok Soy 200. I didnt believe the aged r-value of 7.4, but that's what the technical data sheet and the ESR says for it at 1 inch. That's aged 180 days I believe. At 4inches, it was 26.6, so even that is 6.6 per inch. Seems fairly decent, but I can only go by the sales/tech info each manufacturer has.

Here's the ESR:
John Shockney
Posted: Sep 26, 2011 04:57 PM
The damper I would use just has an adjustable weighted arm and costs less than $100 though it does have to be mounted in a stable position. If you are going to pay $400 for dampers you should go the $1000-1500 an HRV should cost plus installation.

You should not need dehumidification in the summer if your HVAC contractor sets up the AC correctly for your house and a dehumid cycle can be added but only works during the AC operation by slowing down the blower speed and thereby lowering the coil temp. if you have moisture problems in the winter then an HRV or dehumidifier would be the only options.

The big “D” has always over stated their R-values and have had a marketing program to spray less foam at higher profits and to compete directly with the fiberglass guys. I turned their dealer program down over five years ago because I could not find any independent studies that supported all their claims and I didn’t believe in their marketing program. Also search the archives here and you will find other “D” customers with problems where not enough foam was sprayed and or odor problems arose. There is also a you-tube video about a customer in FL that had to have their foam removed due to odor in the summer months again I believe this was also due to not enough foam installed.

The report that you linked gives the R-value for the 2.5 inches that you had sprayed at around 16 to 17 that may be fine for walls but I don’t think that will do the job in the southern summer heat if you have a dark colored roof my figures show a summer heat gain of 42BTU’s per hour per 100sqft of roof if you increased the R-value to R-32 it would reduce the heat gain to 21BTU’s per hour per 100sqft. ? How many squares of shingles where used on your roof and what color are they?

Also anyone that tells you that R-value doesn’t mean anything is full of bull,,, just ask your HVAC contractor what he put into his manual-J calculations. It is only the fact that the R-value for fiberglass has been overrated that it has been a problem, when an R-19 batt of fiberglass only performs at R-10 at 20degs. So if you only put R-10 worth of foam in don’t expect it to outperform an R-19 fiberglass wall that is air sealed.

Posted: Sep 27, 2011 08:56 PM
I figured it was the big "D" touting such claims. Bayer's ESR#2072 says 6.9 at 1". It actually states 7 per inch at 2",3",and 4" and then fading back to 6.8-6.9 thru 12".
I'm not trying to diminish your job, just wanted to make sure a better foam had not hit the market. Thanks and good luck with your project.
Bob Silverman
Posted: Sep 27, 2011 09:22 PM
Just out of curiousity, did the contractor sell you on R7.4 per inch, or did he mention that there was a reduction in R-value with greater that 1" of thickness?

Brian Langston
Posted: Sep 27, 2011 09:30 PM
Neither. It's my own fault, but I requested 2lb closed cell foam insulation. I wasn't informed enough to ask for a particular brand.

I'm not disappointed in my selection by any means. 2.5IN in the walls and 3IN on the ceiling is what every foam co. in this area recommended, unless I went open cell. I prefer closed, just out of personal preference.

I estimated about an R6 per inch.

I find it interesting that I see recommendations for even 4IN of closed cell, when every white paper I've seen says there are diminishing returns over 3.5in, at least on a cost/benefit ratio.

Unless one is in an extremely cold climate, where would more than 4in of closed cell be recommended, unless required by code?

You need to login to reply to this topic. Please click here to login.