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1 Answer

Wanted to confirm I have correct understanding:

1. It is ok to have 2 or more air barriers in an envelope assembly
2. It is not ok to have 2 or more vapour barriers, in case moisture got into the wall, it would not be able to dry out.
3. A vendor told me that vapour diffusion only occurs 'in a straight line', i.e. perpendicular to wall or roof. If I have a shiplapped layer, the vapour will not follow the serpentine profile to go in or out of the house.

In General questions | Asked By Jerry Chwang | Apr 2 14
1 Answer

There is thermal insulation in the attic. Is it possible to use NON-IC lights and create a border (kind of fake ceiling), if it is possible, what's the mark spacing between this border and the insulation.

In General questions | Asked By Natalia Lucar | Apr 2 14
1 Answer

I had a question regarding a roof SIP and GRACE Ultra Peel & Stick - Butyl Based Membrane. The SIP has an EPS core and my concern is when a fastener punctures the peel & stick membrane, the rubberized butyl gets into the EPS core. It is a rubberized asphalt type of product. Since petroleum and EPS don't mix, will this cause a problem?

I read that petroleum based products can eat away at EPS and literally melt it. Will this be a problem with GRACE peel & stick on the SIP roof with an EPS core?

In Green products and materials | Asked By Peter L | Apr 3 14
1 Answer

Has anyone tried to quantify heat loss through the outdoor parts
of typical heat pump lineset installations? Does it matter much?
It occurs to me that some token amount of insulation is applied
there, but is it sufficient? Especially on the vapor line, which
runs pretty warm in heating mode and the farther the lineset goes
before coming indoors, the more it's exposed to a high delta.

Trying to ballpark it, assuming typical pipe insulation with about
a 1.5" outside diameter and half an inch thick, what is that stuff
usually, about R-3? Assume a ten-foot length running outdoors to

In Mechanicals | Asked By Hobbit _ | Apr 2 14
4 Answers

I am interested in using your "cut and cobble" method for insulating the walls of my addition. I live in zone 5 and plan to use 2" of extruded polystyrene and 4 1/2" of dense pack cellulose. Are there any negative effects in using readily available uncoated extruded polystyrene with a perm rating of 1. ? The coated extruded poly seems to have a perm rating of .1 but I cannot locate any ( Dow is no longer making it).

In Energy efficiency and durability | Asked By Rolf Reiss | Apr 2 14
3 Answers

On the attached truss drawing, I used pink highlighter to accent the areas of rigid foam. For the knee walls (technically full height) I was planning on using cut and cobble for the thickness of the 2x6s and then a continuous 4" layer of EPS on the inside just prior to drywall. Seams would be staggered and taped.

On the bottom of the bottom chord of the truss I was planning on a continuous 2" layer of EPS.

All attic portions of the truss would be blown cellulose. The bottom 2x12 truss that spans 20' would be blocked at both ends with rigid foam and then dense packed with Spider.

In Energy efficiency and durability | Asked By Rick Van Handel | Apr 1 14
6 Answers

I am researching the use of EPS and XPS in sub-slab applications for standard residential housing. Thus far it appears as XPS is winning the battle here in the US but I hear that in Europe, EPS is the dominant product of choice. I would love to get some sources to confirm this and to find out "why" Europe ended up going towards EPS over XPS ... I have my suspicions but in data I trust!

Based on the data and research I have found (mostly from product manuf. and some independent studies), I have drawn the following conclusions:

In Green products and materials | Asked By Colby Swanson | Apr 2 14
2 Answers

I am purchasing a house with a geothermal heating and cooling unit already installed, but I would like to make my house more energy efficient. I was thinking about replacing my current water heater with a tankless electric one as my house is not serviced with gas. I am, however, not sure if the two systems would be compatible or if it would even be wise since my Geothermal is run into my hot water heater.

Any advice would be helpful as I am a first time homeowner, and want to be as responsible as possible.

In General questions | Asked By Marc Sinclair | Apr 2 14
35 Answers

I'm looking for advice (and a little comfort) for the following situation:
We are in the process of building our own home... slowly.

Our exterior wall as designed is as follows:

Wood clapboards
1x strapping
felt paper
2" foil faced polyisocyanurate insulation (taped joints)
1/2" plywood sheathing (taped joints) (dedicated air barrier)
2x6 stud walls with Roxul batts
1/2" gyp bd, painted

We have all of the ductwork in place for an HRV, but it is not yet installed.

In Energy efficiency and durability | Asked By Heidi Davis | Mar 7 14
6 Answers

OK, I'm hoping you will all take a crack at this so I can compare your numbers to mine!

I need to estimate the energy savings that would be achieved from taking an uninsulated basement wall of a home in Spencer, Iowa and insulating it to a total R value of R13 using either XPS or spray foam that would would be framed and covered with drywall to meet code. Assume NO additional insulation in the stud cavities.

Here's the details of the home:
Ranch home, 1538 square feet of basement space. Total wall square feet is 1,288 sq ft.
Basement is conditioned.

In Energy efficiency and durability | Asked By Curtis Dean | May 13 11
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