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11 Answers

Advice on Insulating Unvented Attic - 1884 Home in Zone 4A

I hesitate to ask a question on this topic knowing how many other threads exist. I hope my question is OK. I have spent considerable time on forums such as these and read many articles on sites like Building Science. I am struggling with making the right decision on the insulation.

In Energy efficiency and durability | Asked By Historical Work | Sep 15 12
5 Answers

Insulated Roof Questions

Hello All
I have a 1910 house, 1-3/4 story in Denver, CO (zone 5b) with an unfinished attic. The insulation on the attic floor needs to be increased. My roof is getting old and will need to be replaced soon as well. I’ve been reading about adding rigid insulation to the roof, which sounds appealing since the attic doesn’t cover the entire upstairs, but have a few questions:

In General questions | Asked By Patrick McNulty | Sep 11 12
4 Answers

Can Polyiso be applied in a remodel on the exterior of a building without creating moisture problems?

This is a house located in the mixed climate of Virginia. It is currently sheathed with OSB over 2x6 walls. The walls are R19 batts with paper vapor barrier to the warm side. Can the siding be removed, PolyISO applied, furring installed and new siding be installed without creating a mold and moisture nightmare. Removing all the drywall and applying a vapor barrier directly to the inside of the studs is not an option.

In Energy efficiency and durability | Asked By Rick Hyatt | Sep 18 12
1 Answer

Costs and performance characteristics for gas boilers and absorption chillers


I'm doing some research comparing various technology solutions for heating and cooling.

What I'm lacking is cost curves and performance characteristics for gas boilers and absorption chillers. I would like to have the costs and efficiencies for condensing and non-condensing gas boilers at, say, 50kW, 100kW, 200kW, 500kW and 1MW. And costs and efficiencies for single-effect absorption chillers at, say, a couple of hundred kW cooling capacity upwards.

I've found some data on gas boiler costs in some UK references but only for a small number of sizes.

In Mechanicals | Asked By David Coote | Sep 18 12
2 Answers

A little experiment with indirect HW heater

SO there was some discussion about the relative efficiency of indirect water heaters some time back.

It made me wonder, and I had the opportunity to check out the costs associated with standby losses in my system. The family was away for 28 days, so I could shut off the boiler, but that would be boring, so I decided to see how much energy it wasted creating no hot water.

The system:
Buderus GB125BE condensing oil boiler
Superstore SS 60 60 gallon tank

In Mechanicals | Asked By Keith Gustafson | Sep 17 12
2 Answers

Experience with carbon footprint modeling for construction?

Anyone have any experience using the Athena Institute Impact Estimator? I'd like to model alternative construction scenarios to see how much impact each has on reducing the carbon footprint of design elements, material and system choices. Need some help navigating the tool.

In GBA Pro help | Asked By Miki Cook | Sep 15 12
5 Answers

Roof vent baffle - foam worth it over cardboard? vb?

Do plastic baffles cause moisture accumulation issues?
I could think they would trap moisture on the wrong side.

People seem to like to either buy the plastic baffles or construct rigid foam baffles but are cardboard baffles better.

In General questions | Asked By Nick H | Sep 15 12
1 Answer

Zero / low VOC paint and stain

My contractor's painter only uses Frazee paint. He will charge me $1600 more to use zero VOC vs low VOC Frazee paint (which is standard in California). He prefers not to use zero VOC paint and said that it does not last as long and you end up having to repaint sooner which is not good for the environment. If I go with the regular low VOC paint, how long does it off gas ($1600 is quite a bit plus the potential of repainting a few years later)? If you know other brand work better, I will try to convince him to use a different brand.

In Green products and materials | Asked By Rian Bart | Sep 17 12
5 Answers

Below grade insulation/waterproofing

I'm hoping for some advice on my proposed waterproofing plan. I have a 60 year old house that has a small leak in the basement and I expect to see more leaks as that the house is built into a hill and there seems to be a lot of water in the soil against the bare concrete foundation.

In Green building techniques | Asked By Mark Fredericks | Sep 17 12
5 Answers

Should sub slab insulation either EPS or XPS be placed above or below the sub slab vapor barrier?

We will be using ICF's with an 8" core, using a capillary break on top of the footing. Sub slab insulation will consist of 2 layers of 2" foam board with offset seams. Sub Slab Vapor Barrier will be Vapor Block 10 type A.

In GBA Pro help | Asked By Jason Macdonald | Sep 16 12
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