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36 Answers

Stacking SIPs and nailbase for superinsulation

I have a passive house project in the Colorado Rockies and need heaps of insulation to make the numbers work (R-90 walls, R-120 roof). A local supplier has polyurethane SIPs that come in at R 6.66 /inch, however only to a dimension of 8.25" thick for approx R-50 for the 8" panel. I had thought about stacking nailbase SIP from the same manufacturer on top to achieve my R value, but my brain sounded alarm. There would be a layer of OSB that can't "breathe"-this seems bad.

In Energy efficiency and durability | Asked By Erik Lobeck | Feb 24 12
1 Answer

Cathedral ceiling rigid foam vents?

New construction -- having the attic trusses built with 18" top chord for insulation and baffles. Not totally sold on spray foam.

The question is: doesn't building vents with foam or using plastic vents that are sealed to the truss create an area of condensation (it shouldn't condensate with that much insulation)? Or at least, in the event it did get wet, doesn't give it the ability to dry to the outside?

The drywall inside will be sealed and there is only one roof penetration design for plumbing vent.

In Energy efficiency and durability | Asked By jeff ANDERSON | Feb 29 12
1 Answer

Site upgrades going on now

Hello all,
We are in the process of adding a couple of features to GBA and tweaking some of the styles. You will likely notice a few glitches as we move code from the development servers to the live server.

You can report problems here if you wish. We should have this first phase of upgrades complete sometime tomorrow, but you never really know how things will flow.

Thank you for your patience.


In General questions | Asked By Daniel Morrison | Feb 29 12
9 Answers

Are there efficient in-slab radiant systems that also cool?

A client is getting bids from HVAC contractors to design/install heating & cooling systems for a 3100 SF single-level home located in the high desert climate of southern Utah (think Alburqurque, NM). The bids are quite high, perhaps due to the fact everyone says the client will need TWO complete systems; one to heat, one to cool. The bids all specify in-slab boiler-fed hydronic radiant heating coupled with a standard forced air furnace with a conventional AC unit for cooling (and I guess back-up heat). A friend keeps saying: "Screw that!

In Mechanicals | Asked By Timothy Smith | Feb 28 12
4 Answers

Is this a durable roof assembly?

I am working on the details for the roofing assemblies of two houses which are modeled in the PHPP to meet the Passivhaus Standard. We are in the Sierra foothills of California.

For the roofs, I am planning on metal roofing, over 3/4 furring strips, over 2 layers of EPS with staggered and taped joints, over Grace Ice and Water shield on plywood roof decking. The rafter cavities are insulated with cellulose and the assembly will dry to the inside.

In Energy efficiency and durability | Asked By Mela Breen | Feb 28 12
1 Answer

Radon and Sub Slab Drainage

Asked this over at JLC, I am still interested in opinions on question and comments...

I am going to use the formadrain in a few weeks. I am going to use the interior formadrain for radon abatement (interior formadrain connected to a 4' PVC passive system to vent out the roof at first, then fan driven if the radon numbers come in high after the house is completed).

In General questions | Asked By Joseph Garten | Feb 29 12
15 Answers

What's wrong with this wall?

From inside out...
1/2" Drywall
2x4 framing
Diagonal T brace or let in 2x bracing
2" XPS caulked and taped (doubles as WRB)
Horizontal Furring strips
Extira Siding

2x4 framing w/ 2"XPS makes window bucks easy. Extira (exterior grade MDF) is the probable siding choice as the desired look is approx. 2'x4' panels, and smooth texture is preferred. Running the furring strips horizontally allows the panels to be fastened in a location the makes sense for the panels, as well as allowing some customization of panel size. What am I missing/overlooking

In Plans Review | Asked By Aaron Vander Meulen | Jan 3 12
3 Answers

A question about Guardian UltraFit DS blown-in fiberglass insulation

A insulation contractor gave me the option of a wet spray blown-in fiberglass product. Made by Guardian, UltraFit DS appears to be applied like wet spray cellulose. Any insight, pros/cons would be appreciated.

Home located in North Central Washington State. Climate zone 5.


In General questions | Asked By Thomas LaCrosse | Feb 28 12
5 Answers

Dedicated ERV system and Bathroom Exhaust

We are designing a dedicated ERV (recouperator) duct system in a high efficiency remodel. The question has arisen regarding the bathroom exhausts and whether we can utilize the ERV exhausts in each bathroom and a booster switch (dual function timer) in lieu direct vent bathroom exhaust fans. Thoughts? Ultimateair does not to take a strong position on it in their literature.

In Mechanicals | Asked By Patricia Shields | Jan 2 12
1 Answer

Radiant Floor Heating Efficiency

I have a brand new home in Northern Virginia. The home has a 9' high full in-ground basement that is currently unfinished. I am wondering when we decide to finish this in the coming years what is the most efficient way to do so.

In my experience the basement tends to be cooler or cold and damp. We should have adequate drainage through the drain tile system, sump pump, and foundation water proofing.

In Green products and materials | Asked By Shaun Kennedy | Feb 28 12
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