Spray Foam in Attic (Woodland: renting, how much, home builder)

[jdbiron]

I just signed a contract to do a new construction in Shadow Brook (in Monrovia). The builder (Woodland) has offered me an upgrade of doing Spray Foam in the attic for insulation (unvented roof).

Looking for answers for a few questions

#1 How much should it cost for a 2300 - 2400 sq ft house.

#2 What kind of energy savings can I expect.

#3 What are some pitfalls to having an unvented roof.

#4 Has anyone had this done?

[Mawoods]

Our builder Barry Phillips put it in our spec house. Have had it a year and so far no problems. I do think our energy costs have been very reasonable but it is hard to compare because we downsized with this home. It is nice to be able to go up there and put things in storage without burning up or freezing. I believe the product we have is Icynene (not sure of spelling). Our was already in but I believe that somewhere I heard that it cost about 10 -14 grand for our house which is about your same size square footage. I would get a cost from an independent vendor who sells it - and not trust the builder to tell me what it cost. They can pad that I believe and I think that Woodland might do that. With your cost quote you can negotiate better.

[Toymeister]

I saw that in one of their homes. The insulation is on the underside of the roof sheathing. What I saw did not have stanard insulation in the ceiling. So you are heating and cooling the attic. I do not see how this makes any sense. Consider this: If an unvented attic makes sense why is it not the norm? Certainly it is not a state secret. I say every other home builder in America has it correct and Woodland is wrong. If you disagree how do I have it wrong?

Certainly that makes for a really great attic but (newsflash) I don't live in the attic.

I calculate that based upon Mawoods lower estimate of $10,000 I can heat and electrify my 3200 sq ft home for 3 years. That is ALL the cost. So lets say it is somehow more efficent to heat the attic and it saves 20% -and this would be some feat- then I will pay for the 10,000 insulation in 16.5 years. All I can say is I sure home you enjoy your attic!

Oh because some here love to post links here is a link on this construction process http://www.buildinggreennc.com/files...ray%20Foam.pdf

[Mawoods]

We are not heating or cooling the attic. No vents go up there. The Icylene keeps the attic that comfortable.

And I believe I have seen several shows about this product being the next state of the art for insulation.

[Toymeister]

You are heating directly or indirectly all parts of the home until the point where there is insulation from the outside. Insulation may be wood, brick, spray in insulation, fiberglass and so on.

Your home, indeed all homes, have areas that have direct heat (heat vents) and areas that are indirectly heated. Those indirectly areas of the home are 'comfortable', because they have heat or cooling leaking into them. Your attic is 'comfortable' because you are heating it. Mine is 'uncomfortable' because I am not.

You are hearing how great spray in insulation is at home shows because they are SELLING IT. There are several applications where spray in is your best option as the link I already posted shows. A 'standard' attic above a room with flat ceiling is not one of them as it is not cost efficent.

Yes it works because it is insulation, it is not efficent for an attic that accesable roof because you are indirectly heating and cooling your attic. That is not an opinion that is a fact: the laws of physics are the same in in your home as they are in mine.The drywall in your ceiling leaks heat and cold just like my drywall because drywall is a poor insulator. It does not matter that all air gaps are sealed in your ceiling or the HVAC ducts in the attic are nearly air tight: the heat and cold leach through your ceiling into your attic. Your heat rises to the roof where the insulation is while mine stops just above the ceiling where the insulation is.

Look I get it Maywoods you like your home and I am happy for you, you like your insulation and that's great. And don't take this as a bash, its not, no it is not cost efficent to use this insulation for most applications because of the laws of physics.

[mlenox17]

There are more issues than whether or not you are cooling the attic. Moisture that condenses on cool ductwork that runs through a typical vented attic is one issue. The cooling lost from these ducts into the non-insulated attic is another. With insulation on the outer skin, no moisture gets in and all ducts are inside the insulated area. (Conversely, there is no way for moisture to get out of the attic either.) Further, the insulating properties of the sprayed foam are much different (higher R value, better sealing of gaps) so you are not comparing apples to apples.

Do not give much merit to conventional wisdom on ventilation for the attic and even less for the crawl space. In the South, problems from warm, moist summer air being vented into these spaces where ducts, pipes and outer walls are cooled causes myriad problems. Insulation dampened by condensation becomes almost useless. Mold and wood rot are even worse. Get all the facts.

I do not work in the construction industry.

[jdbiron]

I've gone out and done some research.

The most vocal expert on unvented ceilings is Joseph Lstiburek (PH'D in Building Science - Indoor Air quality expert ASHARE Fellow) He has done many studies including a study of unvented vs. vented ceiling in Los Vegas NV: BSD-102: Understanding Attic Ventilation —
In his top 10 dumb things to do in the south he puts a vented ceiling at #10. His main arguments are: #1 HVAC units are usually put in the attic - thus there is potential loss of conditioned air if they leak.
#2 The air outside is humid thus letting it in the attic is not a good idea. Also vents allows for rain water to get inside the house.
#3 If done right there is only at most a 5 degree difference in shingle temperature between the vented and unvented roofs. Also many shingle manufactures are warrenting correctly installed spray foam insulation.
His full list is here Joe's Top Ten :: Joseph Lstiburek

As far as energy efficency i have heard at least 20% - since air does not escape the house it costs less to heat and cool the ac (even with conditioning the attic) - reference the Los Vegas study above. The foam does have a higher R value as well as it serves as a moisture shield and air barrier.

Added benefit is that storage in the attic is much better now. Vented attics can have temprature swings of 130 - 140 degrees to below freezing. Unvented your within 5 - 10 degrees of your house.


As far as why is it not standard - it seems to be catching on - new technology takes time to become standard.

As far as woodland goes - it is not standard in their houses (they have only done it on one house so far) They said the energy savings between the spray foam house and the typical insulation was pretty dramatic (>20%). They havn't given me the price for the upgrade yet but they did say it would be pretty pricey. (Less then 10k though)

[jdbiron]

Originally Posted by Toymeister

Look I get it Maywoods you like your home and I am happy for you, you like your insulation and that's great. And don't take this as a bash, its not, no it is not cost efficent to use this insulation for most applications because of the laws of physics.

Tonymeister - i do understand that you are conditioning the attic indirectly, but studies (that i reviewed) do show 20% savings over a vented attic. The only difference would be if your HVAC unit is not in the attic. Then the savings is less.


As far as ROI - depends on how much the investment up front is. Right now I'm assuming 6 k for up front investment - it would pay off in about 10 years. Not sure if this will help re-sale value of the home, but lower energy costs combined with good attic storage space may boost the re-sale a little bit (maybe not 6k but 1 - 2)

[Toymeister]

Originally Posted by jdbiron

Not sure if this will help re-sale value of the home, but lower energy costs combined with good attic storage space may boost the re-sale a little bit (maybe not 6k but 1 - 2)

It is unlikely you will get even 1.00 back on sale. Americans care more about the color of the paint than structure. I say if you have done due diligence then go this way, as you have. For me I added attic vents (most homes have too few) and more insulation, all for well under 500.00

[jdbiron]

Originally Posted by Toymeister

It is unlikely you will get even 1.00 back on sale. Americans care more about the color of the paint than structure. I say if you have done due diligence then go this way, as you have. For me I added attic vents (most homes have too few) and more insulation, all for well under 500.00

That's a very good point. The only way it would add resale value is if the electricity bill is dramatically less which I'm not sure if this will or not. After doing due diligence I'm still on the fence for two Reasons.
#1 Its expensive
#2 Its still fairly new so there still could be kinks that have not been realized yet.

There are Pros and Cons with everything. Have till Monday to make the decision. I'm not sure if there really is a "Right" decision here.