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93 Answers

Explain the correct usage of rigid insulation on the exterior of the building.

Rigid insulation seems like a good choice to add R-value to the whole wall (breaking the thermal bridging, etc) as opposed to just between the studs like most insulation. But isn't it basically impermeable and thus not allowing the wall to breath...not allowing moisture from the inside to exit by diffusion.

In Energy efficiency and durability | Asked By Conrad Welch | Nov 3 09
7 Answers

When am I allowed to open windows?

Opening windows...is this permitted anymore? Most houses have 'em. Are we allowed to use them anymore?

In General questions | Asked By Dennis Dipswitch | Mar 30 13
3 Answers

Cedar shingles over foam board?

1940's cape with vinyl over shingles in zone 5a zip 02452. Considering stripping the front of the house and putting typar, then at least r5 of foamboard. Question: Is it possible to put shingles over the foamboard? Just use longer staples? Any problem with having exterior foam on only one side of the house? It's the south side.

In General questions | Asked By stephen edge | Apr 2 13
3 Answers

Sloped ceiling insulation

In climate zone 5 we have renovation of a cape home and a suggested sloped insulated roof design as following:

Soffit to ridge ventilation with baffles the entire way. Blown in fiberglass insulation in 2x8 rafters 16 oc. Underside of rafters covered with 1.5" Thermax under the entire roof.

Question: Where is my dew point in this assembly and are their any concerns with this type of air barrier and insulation design?

In Energy efficiency and durability | Asked By Flemming Lund | Apr 2 13
3 Answers

Straw bale retrofit?

Hello, I would like to insulate the exterior of my 1940's prefab with straw bales. Has anyone done this? If you have, could you advise me of the best way to tackle it?

Thank you.

In General questions | Asked By David Flint | Mar 23 13
8 Answers

Coastal considerations

Looking to build a small, age-in-place cottage down in Rhode Island. It's across the street from a bay and faces west. I'm thinking the west side will have a good ammt of windows and will be the gable end. Solar opportunities on the south facing side.

It gets really windy there, so I'm wondering what type of insulation scheme we should persue. Or if the wind factor changes your approach at all. I'm also wondering if we should build on piers.

If there are any green builder architects in RI coastal work you can recommend, it would be appreciated.

In Green building techniques | Asked By stephen edge | Mar 29 13
1 Answer

Wedi replaces green board and cement backer?


Any thoughts on the use of the Wedi or Fundo systems? Looks like puting it over drywall will make a bathroom stand up better to bulk water, spray, and condensation. Also seems a better substrate for tiles than green board, cement backer, etc. My thinking is to use it on the walls and celing of a mechanically vented bathroom.

In General questions | Asked By Oak Orchard | Apr 2 13
4 Answers

Support slab or not support slab?

I have designed an ICF wall with an insulated slab supported on one edge as described on this site and also Building Science's paper "Slab Happy". See drawing below.

My builder doesn't like this because of the extra labor and material costs and concerns about the slab on the edge of the stem wall, possibly leading to cracking

He prefers to not support the slab and let it float within the stem wall as per drawing two. I am concerned that this is more prone to movement and cracking if there is any settling.

Both would have compacted soil and some sand or gravel underneath the slab.

In Green building techniques | Asked By Stephen Carlton | Apr 1 13
2 Answers

Snow load on PV panels

Where I'm planning on building the code requires design for 75 PSF snow load.
The best rating for load that I've found in PV panels is 40 PSF. In the unlikely event that an actual maximum snow load were to occur some of the panels may fail but no other structural damage would occur. Could such a situation be approved?

In Building Code Questions | Asked By Jerry Liebler | Mar 28 13
11 Answers

Icynene & moisture

OK some of you may remember my previous question/story about Icynene, we now have more data and more questions;-)

Here's the beef:
I am removing Icynene OC foam from under the roof because it still stinks but here's something that's very odd.
It's a 1920s house with wood planks all over, a new metal roof installed right over 3 layers of self adhering premium underlayment.
Icynene was sprayed 6 in underneath deck to fill the rafter space about 1.5 years ago.
Now, here's what I measured.

In General questions | Asked By Don J. | Apr 1 13
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