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8 Answers

Foil-faced polyiso for site-built baffles

First, thanks to everyone here for all of the advice and knowledge I've gleaned as a reader for the past year.

In GBA Pro help | Asked By David Baca | Dec 31 12
4 Answers

Rigid Foam Board in Crawl Space, Zone 3

I have a client in Zone 3 whose home is suffering from extensive air infiltration through the diagonally run dimensioned 1x subfloor that is covered with T&G hardwood flooring. The homeowner shows very little interest in encapsulating the vented crawl space and adding a dehu, and I cannot convince them to use SPF in their crawl space floor cavities either. They have read an article that suggests the installation of rigid foam board @ the bottoms of the floor joists.

In Energy efficiency and durability | Asked By Chris A | Jan 14 13
4 Answers

Attaching Insulweb to wall penetrations and preventing cellulose blow-out


(1) My ceiling: 24" o.c.12" deep rafters/cathedral; I have already installed 1/2" low-sag Sheetrock glued and screwed horizontally.

(2) My walls: 24" o.c. Larsen trusses.

(3) No top plates; Larsen truss wall bays pass directly up into the rafter bays. It's a cantilevered pole construction; building load hangs on 3/4" rod attached to poles (i.e. 6 X 6 square timbers)

(4) No basement: plumbing and heating PEX, wiring, etc. are in the walls; Stelrad radiators used for heating.

In General questions | Asked By Oak Orchard | Jan 10 13
3 Answers

Metal building and condensation

I got a call from a friend Friday. He was asking me about a metal commercial building that was having a problem with condensation on the underside of the roof. He had not been out to see it yet so he did not have all the details.

From what I gathered it didnt have insulation against the underside of the roof. There was an insulated flat ceiling with an air gap above. Supposedly not much room in between.

Does a metal roof require the insulation in contact with it to prevent the condensation. Or if the air barrier is improved will venting do the trick.

In General questions | Asked By Robert Hronek | Jan 14 13
3 Answers

Humidity issues....suspecting brick foundation

I am more or less done with the energy aspects of a deep energy retrofit (DER) of my home (built in 1910) and now experiencing humidity issues. I am in NY in zone 5A. This is going to be a very long post as I am trying to get as many details as possible.

In Energy efficiency and durability | Asked By upstate ny | Jan 14 13
3 Answers

Proper use of multi-split heat pump

We recently had a multi-split heat pump system installed in our home in CT (5a). We have one head upstairs, one that feeds the kitchen and living room on the main level, one that feeds a back room on the main level and a mini-split wall unit in the lower level rec room. We were a little bummed to find our energy bills after the first month didn't really improve - our oil bill went down, but our electricity bill went up so much that it canceled out any savings. I am wondering if we are not using our system as efficiently as possible.

In General questions | Asked By Chris Heinen | Jan 11 13
5 Answers

Sizing an HRV

I am working on sizing an HRV for my son's house. Using ASRAE 62.2 I get 77cfm. Using ACHnatural of .35/hour I get 144 cfm. Using Venmar's tables I get 160/80 cfm for the high/ low. Using 10 cfm/room and 20cfm for master bedroom and basement I get 180 cfm. I wonder if some of the higher numbers from the manufacturers are trying to account for high speed venting of bathrooms. However I wonder even at 180 cfm with ten supply and return grilles if he HRV can pull enough air out of one bathroom to stay ahead of a long hot shower on a cold winter's night.

In Mechanicals | Asked By Steve Kent | Jan 13 13
1 Answer

Internal Insulation of Masonry Walls

I am renovating an Brick Home in Toronto. The exterior walls are Load bearing brick walls with some parging, furring, and plaster board. I want to add insulation on the interior using the wall assembly described on page 24 of the pdf guide "Internal Insulation of Masonry Walls: Final Measure Guideline" see below for URL. I have a question about this assembly... I noticed that there is no vapour retarder, should I install a vapour retarder on the warm side of the insulation between the insulation and the wood studs?

In Green building techniques | Asked By david lam | Jan 14 13
2 Answers

ERV ducting - how to insulate?

We have an ERV, which works great for our house, which is in a cold climate (i.e. this week will be below zero at night for the next four days, and teens during the day). This is our second winter in the new house. We have discovered that due to location, a hot water line (PEX with R-4 insulation) crosses over the ERV incoming duct in the between-floor truss level. It has frozen at this point.

In Mechanicals | Asked By Richard and Miranda Menzies | Jan 12 13
6 Answers

Insulating a scissor truss

When insulating an unvented scissor truss roof with loose cellulose, ~24" heel height and ~ r-30 spray foam against the underside of the roof decking, can I leave an increasing airspace as I work my way up to the peak? In other words, I want a consistent thickness of cellulose (~18") starting from the raised heel up to the ridge. Can the remaining space between the cellulose and spray foam be a air space or am I risking condensation somewhere in the sandwich? This is assuming air barriers at the roof decking level and bottom chord. BTW: Zone 7-8. Thanks.

In Green building techniques | Asked By Matthew Michaud | Jan 12 13
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