Insulating and confused

cathyckJune 8, 2012

We are building a home about 20 miles north of Manhattan. We have varying opinions on what should be done with the insulation and the actual installation we stopped while they were installing yesterday. Code is R38/R19. We settled on R38/R21 on top of 1/2-1" spray foam to seal the house. We were never told there would be problems with possible moisture, but 2 days ago, the guy that recently came to work for the insulation company (that tried not to honor the quote and was rude and arrogant)told us that we should do all foam if we do one on top of the other,and that there would be moisture problems .HE said they could spray the walls but not the ceilings or attic. Our ceilings are cathedral and high, or 9'. What do we need there, and in the basement ceiling? What is the truth? We have a contraflow masonry heater fireplace also. Please , what do we need to do for good, reasonable efficiency and air sealing? Do we need a ERV, would that help? This has never even been mentioned. How much are those? What about a blower door test? Where do you get those and how much do they cost? Thanks for all your help, I'm frazzled!

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Specify one inch of spf and you should not experience moisture problems. Whether a hybrid system is the most cost efficient is another question. See here (Scroll down to Figure 6.)

For an unvented cathedral ceiling, the only effective choice is spray foam or extruded polystyrene above the roof decking. Dense-packing an unvented cathedral ceiling is asking for certain trouble.

HE said they could spray the walls but not the ceilings or attic.

That's ridiculous. Unless, of course, you've already dry-walled the ceilings.

The basement is part of the conditioned space of the home; there's no point or need in adding insulation, other than for sound attentuation.

An ERV or HRV is a good idea in a heating climate such as yours.

All these decisions should have been made in the design process in consultation with your architect or designer.

    Bookmark   June 8, 2012 at 9:56AM
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To clarify:

there's no point or need in adding insulation on the basement ceiling.

    Bookmark   June 8, 2012 at 10:38AM
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Thank you Worthy. This whole building has been a whole fiasco, but that's another story!Our architect said we would do it as we went along. I didn't know that it would be the architects job to tell us what we need to put in. He hasn't given us advice on any of that. We have had 3 different plumbers and gotten taken for a ride. The ac guy came out without even talking to me and put in the ac without even discussing what type, where to run the ducts etc... My husband just keeps seeing $$$ signs and won't let me change it or say anything because we supposidly got the best because the guy owed him a favor. I think we paid too much and it wasn't what I wanted.I don't even know much about it and he put in 2 units-. We have radiant heat, which was supposed to be tied into the contraflow heater to heat the house but the plumber didn't do it either.

    Bookmark   June 8, 2012 at 10:55AM
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Epiarch Designs

Worthy gave good info. Spray foaming rarely pays off, but in this case the cathedral ceiling is probably your only option. Code states the need for a vapor barrier, and closed cell foam is about the only way to achieve that at this point I assume. (note I said CLOSED cell, open cell will not qualify unless they use an expensive thermal barrier paint on the foam. It will also not meet IECC most likely for ceiling insulation).

Touching on your other questions- An HRV would be ideal for your climate. Any time a home is tighter, you need to have mechanical ventilation installed. They are not terribly expensive, and run between 1-3k depending on the size required and if you go with dedicated ducting (more efficient).
A blower door test is a good idea to confirm air sealing and tighness of the home. Anything below 3 air changes is a good starting point, but less is much better. They are typically not very expensive, around here they cost around $300-500. That money is well worth it assuming they will find leaky areas in the house that will rob your heating and cooling for years to come. Air sealing is more important then insulation, as insulation (with exception of spray foams) does not air seal. Caulking is much cheaper then spray foams.

    Bookmark   June 8, 2012 at 11:56AM
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Look up flash and batt.

Fine Housebuilding had a good summary article a few moths ago.

The foam can provide excellent air sealing, while using batt to raise the overall rating is often cost effective over a full foam job.

Part of the 'trick' is to make sure the frost point stays withing the foam layer.

    Bookmark   June 8, 2012 at 3:06PM
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