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3 Answers

Replacing R410a minisplit: Lineset cleaning, pressure testing, and purging

Should I use a cleaner designed for converting from R22 to R410a linesets to clean a lineset that will only replace a R410a mini split?

I am replacing a 7.5 year old Samsung 1 ton unit with a Fijitsu 1 ton unit. These are both single units. They both require 1/4" and 3/8" lines.

I've gotten mixed answers from many HVAC professionals on this question. It seems like the wild west here in Wisconsin on mini-splits (and other HVAC subjects).

In Mechanicals | Asked By Resilient_Kevin | Jun 14 18
1 Answer

Reuse old fiberglass batts?

We are gutting and rehabbing an old house. We are pulling out the old fiberglass insulation from the walls and ceilings, and we have quite a large collection of the batts. Can the insulation be reused?

Some of it is obviously in bad shape, but a lot of it is still fluffy and pink with some discoloration. I know the batts acted as an air filter for the (very) leaky house over the decades, and so they have collected dust and dirt.

How much has that degraded the effectiveness of the insulation? Would it be worth salvaging some of the insulation?

In Energy efficiency and durability | Asked By James Fugate | Jun 18 18
14 Answers

Roof / wall connection showing vent above structural sheathing

I know this has been discussed a thousand times here but each situation is unique and I find that answers seem to vary depending upon the mood of the commentator.

I had previously developed a similar detail as the one shown which had furring strips below the sheathing allowing the vent channel to run below the sheathing but I believe this introduces a whole host of problems not the least of which is an area of loose fabric above my dense packed rafters which overtime could become home to a whole host of critters which might then crawl though it.

In Green building techniques | Asked By Ethan T | Jun 15 18
9 Answers

Has anyone built a south-facing roof on a building that's 45 degrees off?

I have the opportunity to add an attached garage to my house, and I'd like to provide a plaftform for solar PV on the roof (Zone 5, NW Ohio). The existing structure (and the entire town) is oriented 45 degrees off; that is to say, the street runs northeast/southwest. I'd be attaching the garage on the side of the house that faces southeast.

In Plans Review | Asked By Andy Chappell-Dick | Jun 16 18
2 Answers

Second Heating and Air

Where would be the best place to install the second unit (basement, 1st floor, upstairs)?

In Energy efficiency and durability | Asked By user-7084153 | Jun 16 18
6 Answers

Horizontal roof strapping for ventilation?

I am building a 16'x24' house in Alaska, 12/12 gable roof using 2X12 rafters, with a cathedral ceiling. A friend has recommended venting the roof by strapping the rafters horizontally with 2x4's at 16" o.c., thereby allowing cross ventilation from gable to gable. The roof would be sheathed on top of the 2x4's. I haven't been able to find any information on this technique on the web.

In GBA Pro help | Asked By Justin Smith | Jul 15 13
4 Answers

Load calculation questions

We have just hired a ResNet rater to complete room by room load calculations in our new home (CZ4, humid), prior to interviewing HVAC contractors.

The first load calculations are about 73k BTU peak heating for the whole house. Our goals are thus 1) confirm model inputs and 2) identify envelope upgrades to lower peak heating load to 60k, so we can pursue a 5 ton air source heat pump. We'd consider zoning but are not sure hoe much this would increase efficiency or comfort with ASHP.

We like and trust the rater, just confirming a few things with the experts here:

In General questions | Asked By FrankFulton | Jun 15 18
9 Answers

Double Stud Wall & Basement Insulation Review - Climate Zone 5A

I've read practically every article on this site and many others related to 2x4 double stud walls and moisture. I want to have a wall that is low risk for moisture issues without introducing any more expense and complexity than necessary. The following seems attainable with my budget, and doesn't seem to cause much builder concern for construction. From exterior to interior:

LP Smartside Siding
1/4 rainscreen composed of either a mesh or furring strips with an insect screen at the bottom
Tyvek Drainwrap
CDX Plywood, seams taped

In Energy efficiency and durability | Asked By Shane | Jun 15 18
1 Answer

Good advice for Florida homeowners with air conditioner problems

Curt Kinder is an HVAC contractor who understands building science principles -- and that type of HVAC contractor is, unfortunately, rare. Curt lives in Jacksonville, Florida, and he often posts comments on GBA.

Curt is helping to raise the bar on building science knowledge in his profession. He was recently interviewed by public radio station WJCT. If you want to hear some of his advice to Florida homeowners -- it's good advice -- visit this web site: Going Green.

In Mechanicals | Asked By Martin Holladay | Jun 15 18
5 Answers

Attic and roof stack

Does this seem like it will work? Austin TX, Climate Zone 2A.

From inside to outside. Air barrier at the interior ceilings.

Drywall (or lath and plaster ceilings)
Blown-in Cellulose (~16 inches, but less over outside walls, as no raised heels)
Mostly solid wood board sheathing (from 1950s), one area of low slope plywood (~1.5 in 12).
Solitex Mento as roof WRB (or other vapor open WRB)
Counter-battens (1x material criss crossed)
Metal roofing

In Plans Review | Asked By James Howison | Jun 14 18
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