It's Official

[AzScorpion]

Metal roofs are good for all the reasons mentioned but with the heavy rain and especially hail we've been getting they are LOUD!

The cabin we rented last summer in SD had a metal roof. We had a lot of heavy rain and hail and I didn't think it was all that bad and this was a cheaply built old cabin. I'd think with the roof decking being spray foam insulation it would deaden the sound quite a bit.

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[Fordup]

With spray foam insulation do you need strapping for an airgap under the metal roofing? Seems like condensation could get trapped promoting mold in humid environments.

 

[AzScorpion]

With spray foam insulation do you need strapping for an airgap under the metal roofing? Seems like condensation could get trapped promoting mold in humid environments.

I honesty don't know because once I got the price I didn't look into it any further. I'm using Zip System on the walls and roof which is an OSB with and green waterproofing/barrier applied to it. It replaces Tyvek house wrap and all the seams and sealed with a special tape that has to be rolled on after it's applied. This forms a water and air barrier and once the walls and roof go up the house is water tight without having to side and roof the exterior. I'll still use an ice & water shield in all the valleys, chimney area and all around the first course of shingles for extra protection against leaks and ice damns.

 

[Fordup]

With that zip system the use of low density foam doesn't need an airgap but from what I read medium and high density foams need air gaps under the siding for condensation control. Figured the steel would need it also. I guess the foam installer would know more about requirements for the different roofing materials.

 

[AzScorpion]

With that zip system the use of low density foam doesn't need an airgap but from what I read medium and high density foams need air gaps under the siding for condensation control. Figured the steel would need it also. I guess the foam installer would know more about requirements for the different roofing materials.

I'm using closed cell foam and there's no air gap requirements with it on asphalt and I would guess metal too. You don't use ridge vents either as it's a super air tight space and conditioned like the main house. It'll make a great room for when I'm in the "dog house" with Annie. ?

 

[Stevedbvik1]

I'm using closed cell foam and there's no air gap requirements with it on asphalt and I would guess metal too. You don't use ridge vents either as it's a super air tight space and conditioned like the main house. It'll make a great room for when I'm in the "dog house" with Annie. ?

You can watch old home movies whilst up in the dog house

 

[Fordup]

Wow, I was told by a roofer that putting asphalt directly on a superinsulated roof with no air gap will cause the shingles to hold excessive heat and shorten the roof life. Guess there must be different codes in different areas. Had a friend do just like you so he could go with a geo grid heating and cooling slab instead of a basement with air changing and handling equipment to overcome the tight structure in the attic. His architect used a ventilation mat under the steel because asphalt wasn't recommended.

 

[Chris M]

The science and engineering involved in homebuilding is amazing to me. Even more so the customization for increased energy efficiency.
Is it possible to get a house too air tight or too efficient?

 

[Fordup]

The science and engineering involved in homebuilding is amazing to me. Even more so the customization for increased energy efficiency.
Is it possible to get a house too air tight or too efficient?

There are codes that specify air exchanges in tight houses and great air to air heat exchangers available. You don't want your wife to smell beer, smoke and farts for 2 weeks after a poker game .

 

[5thranger]

I'm using closed cell foam and there's no air gap requirements with it on asphalt and I would guess metal too. You don't use ridge vents either as it's a super air tight space and conditioned like the main house. It'll make a great room for when I'm in the "dog house" with Annie. ?

Correct, with the closed cell foam direct to metal there is no condensation but if they miss an area when applying you will get a drip. When my shop was built, I had it done and one spot was missed, and it dripped like a hole in roof.

 

[Gerder]

The science and engineering involved in homebuilding is amazing to me. Even more so the customization for increased energy efficiency.
Is it possible to get a house too air tight or too efficient?

of course. put a plastic bag over your head and than wrap some duct tape around ur neck… see what happens the next view minutes… ???

 

[Chris M]

of course. put a plastic bag over your head and than wrap some duct tape around ur neck… see what happens the next view minutes… ???

Fair enough.
But I'd imagine it would be difficult to get that air tight.
I would think it important to get fresh air in somehow.

 

[AzScorpion]

Fair enough.
But I'd imagine it would be difficult to get that air tight.
I would think it important to get fresh air in somehow.

You can get them really tight now and there's a company that does AeroBarrier. After you insulate and have everything as tight as you can get they come in and seal everything up, pressurize the house and release a sealant fog (kind of like a airborne spray insulation) into the air and it travels throughout the house plugging up all the small leaks you can't see and missed. This is an extreme and you'll need air handlers to bring in fresh even without doing this.

 

[Cmar]

That's kinda what I would think, unless there's also some kind of sound-deadening material also included in installation?

We have aluminum foil covered tar paper under ours as a sort of insulation, it's not particularly heavy duty though as all Queensland houses leak heat like a sieve in summer, ( probably not a bad thing) and winter (not such a good thing) but we don't get snow. It does deaden the sound of heavy rain or hail a bit but yes sometimes in a bad storm you can't hear the TV, and have to shout in a conversation.

 

[Gerder]

Fair enough.
But I'd imagine it would be difficult to get that air tight.
I would think it important to get fresh air in somehow.

so you have to build in a straw. secure it with filters against bugs etc. put a fan on top to improve circulation. And last but not least, hope that the fan always has enough power. If it has been properly balanced to the ambient conditions and these are as constant as the physicist needs for an experimental setup, everything should be fine and you won't sweat like crazy when the sun shines on your head. In any case, you are nicely wrapped up artificially and shielded from your natural habitat by a layer of hazardous waste that can practically not rot. Unless the woodpecker or the rats destroy everything again and eat holes in your nice plastic bag. Then of course you'll have to start all over again...

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