Q&A: A Forum for Green Building Experts and Beginners

[Click map to enlarge]

Please register for a free account or sign in to ask and answer green building questions.

The usual rules of courtesy apply:
1. Be nice.
2. If you can't be nice, be polite.
3. If you can't be nice or polite — well, please be brief.

To attach a photo or illustration:
Under the box labeled "More explanation," look for the words "File attachments."
Click that, and you should be able to attach a photo.

Thanks for joining the conversation!

1 Answer

Insulating under a hydronic radiant heat under subfloor between joists system

I have hydronic radiant heat set up attached to the underside of subfloor and between floor joists spaced at 16". This set up sits above 1400 sq.ft. of unheated basement and needs to be re-insulated. Above it is the traditional subfloor with 3/4" engineered oak flooring immediately on top. I have been told many different methods to insulate this ranging from reflective bubble foil to standard fiberglass batting with a face to rigid insulation to any combination of 2 or more of these.

In Energy efficiency and durability | Asked By Doug Adler | Nov 28 12
1 Answer

Soffit vent - leave or remove?

I am going to be converting my vented attic to a sealed & insulated attic. We'll be applying spray foam to the underside of the roof deck between the 2x12 rafters, and at the gable ends. It's a simple gable roof, 8:12 pitch. It has a substantial overhang past the exterior wall, with angled fascia and angled soffit panels (i.e. the soffit panels are nailed directly to the underside of the rafter tails, at an 8:12 pitch)

In General questions | Asked By Michael Hansen | Nov 28 12
3 Answers

Too many vapor barriers with a cold (unvented) roof retrofit?

I'd like to retrofit our existing ventilated roof to an unvented (cold) roof per Martin Holiday's musing "How to Build and Insulated Cathedral Ceiling" (http://www.greenbuildingadvisor.com/blogs/dept/musings/how-build-insulat...) and various Building Science articles but specifically the one included in Fine Homebuilding recently. (http://www.buildingscience.com/documents/published-articles/pa-crash-cou...) In the Building Science article Joe Lstiburek provides details on how an unvented roof can be built by insulating above and below the roof.

In Green building techniques | Asked By Andrew Alden | Nov 27 12
7 Answers

Can I make interior thermal shutters for my windows?

I have single pane windows and would like to insulate them. I was thinking I could put some rigid insulation over them as a shutter and then hinge it at the top. I could lift them in the day and hook them to the ceiling and lower them at night. This would provide added value because it would really block out the light at night, provide sound insulation, and will double as a place to pin drawings that the kids make. When I went to buy this rigid insulation, I read a flammability advisory for R Max. Then I checked a piece at home, and yes, it does burn.

In Green building techniques | Asked By PETER SCHWARTZ | Nov 10 12
20 Answers

Heat Transfer Plates for Radiant heat under floor joists

While everyone can agree on certain aspects of radiant heat systems e.g., most of the time PEX tubing is the right choice, there is a lot of divergence of opinion on the use of aluminum heat transfer plates in under joist installations over untreated living space. The closest I've been able to come to a reliable answer is a study done that seems to suggest that they are a good idea (ASHRAE Research Project 1036 "Develop Simplified Methodology to Determine Heat Transfer Design Impacts Associated with Common Installation Alternatives for Radiant Conduit")

In General questions | Asked By Michael schlee | Jan 4 12
5 Answers

Geothermal or AirSource Heat Pump

I'm trying to make a decision on which type unit to go with. House is approximately 1665 sq foot ranch with equivalent walkout (daylight basement). See plan here: http://houseplans.co/house-plans/1236/

In Mechanicals | Asked By Aron Robinson | Nov 24 12
6 Answers

How can I prevent my roof from sweating?

Hey guys... I want to thank you in advance for your time and sharing your experience and professionalism. I live in Vermont. Upstairs, my roof is part of the wall structure. Last year, my roof sweat like crazy. We insatalled vinal in the eaves and proper vented the roof to the attic space. My issue seems to be in the valleys. Since they dont stretch to the eaves, I am unsure how to get ventilation. Right now, there is proper vent in there with fiberglass insulation below. As you can well imagine, the venting isn't cut perfectly and the insulation butts up tight. Will this work?

In GBA Pro help | Asked By Aaron Chapdelaine | Nov 27 12
4 Answers

How do you reconcile continuous insulation requirements with rated assembly requirements?

The application is multifamily construction. We have energy requirements stipulating continuous R-3 insulation, in addition to required cavity insulation. We also have rated exterior wall assembly requirements.

I have not found any UL or GA assemblies that work, nor have I found any SIS product that has been UL tested.

In Building Code Questions | Asked By david nofsinger | Nov 27 12
23 Answers

How bad is it to use polyiso on the deck and spray foam on the bottom?

I am having my "flat" roof EPDM rubber roof replaced, which right now is only insulated by whatever amount of polyiso foam is on top of the deck. The rafter cavities are empty and the ends, only, of those cavities is currently stuffed with fiberglass batts.

In Energy efficiency and durability | Asked By Brian Winke | Oct 25 12
6 Answers

SIP on top of ICF

I am designing a house using 8 inch ICF foundation walls and a ten inch SIP on top of the walls. The SIPs will be 12' high. The main weight in a SIP is in the strand board skins so I want both of these skins to be over concrete even though they sit on top of a 1.5" thick sill plate.

My design is attached. My builder is concerned that if the slab settles different to the ICF wall there will be some imbalance of weight. To try and counter this I have made a ledge on the ICF wall for the slab to sit on.

Does anyone see potential problems or a better way to mount this SIP on this ICF?

In GBA Pro help | Asked By Stephen Carlton | Nov 27 12
Register for a free account and join the conversation

Get a free account and join the conversation!
Become a GBA PRO!