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7 Answers

IECC 2012 leakage test versus the ASHRAE MVR limit

Comparing the two equations is confusing. If you compare the IECC 2012 requirement for 3ACH50 in zone 4 with the MVR equation for a 2000 sq ft home with 8 ft ceilings and 4 beds in zone 4 with the climate N value of 24.5 the IECC cfm is 32.6 while the MVR cfm is 57.5. The MVR is larger than the IECC leakage level. Am I missing something?

MVR=0.01(2000)+7.5(5)= 57.5cfm natural

3ACH50= 48000 cu ft/24.5=1959ACHn/60=32.6cfm natural

In Building Code Questions | Asked By paul scrivens | Apr 23 13
8 Answers

Safely insulating old house with no sheathing

I'm fixing up an old ~1850s home in Upstate NY (borderline zone 5/6). The 1960s and 1970s were not kind to the house, as its original plaster walls were replaced with drywall, and awful replacement windows were installed. The exterior walls were "insulated" with loosely stuffed fiberglass bats, and aluminum siding was placed over good clapboards. No air sealing was done, so the house is quite leaky. The insulation is home to many varieties of insect and small mammal life.

The current walls are constructed as follows:

    In Energy efficiency and durability | Asked By Aaron Birkland | Apr 20 13
    9 Answers

    Dual-fuel high-efficiency natural gas / heat pump systems?

    Does anyone have any experience with or thoughts on the hybrid "dual fuel" natural gas furnace systems that are combined with an air-sourced heat pump (instead of an AC only unit)?

    The intent is for the heat pump to provide heat when its most efficient, but then switch to gas when the outside temperature drops to the point where the heat pump is no longer efficient or effective.

    In Mechanicals | Asked By Jonathan Rich | Apr 21 13
    6 Answers

    Potted plants as thermal mass?

    I have read rules of thumb to calculate the size of a thermal mass as concrete floor or trombe walls ect to take advantage of passive solar heating. Do similar rules of thumb exist to calculate thermal mass of other materials such as soil in large indoor potted plants and trees and a wood stove hearth and mantle? I'm designing a home (Maine zone 6) with south facing (20deg from due south) high SHGC glazing that is 10-12% of the heated floor area. Given that this is at the upper end of what is recommended I'd like to make sure I have enough thermal mass to avoid overheating in the summer.

    In General questions | Asked By Brian Beaulieu | Apr 23 13
    6 Answers

    Call me crazy ... again with the ideas!

    Just a thought i had while using alot of hot water in my shower,
    and i couldn't find any info on the google ...

    It is about mini-splits ...yes again i know i know ...
    Well they are mini, and also installed in split units !!!

    But that is not the point,
    i was wondering, what if one would be to use some kind of " shelter " on the exterior unit
    let's say an opened ( probably bottom and near top ) shelter of a certain size,
    that would feature a glass window toward south side.

    The point would be to help raise the temperature during daytime when sun hits the shelter,

    In General questions | Asked By Jin Kazama | Apr 21 13
    8 Answers

    Geothermal: how to specify and verify performance?


    I am looking at retrofitting my home with a GeoComfort GSHP and was wondering how to specify and verify performance. Other than simply saying the unit should be able to maintain 71F in winter without backup heat and 79 in summer. Are there any specs from a consumer stand point that can be put down on paper and then can be verified?

    The home description is in this other thread (I am in zone 5A):


    In Energy efficiency and durability | Asked By Venkat Y | Jul 23 12
    9 Answers

    Sealing between floors on 1.5 story home?

    High, I am currently building a 1.5 story home with 2.6 walls that will be insulated with blown cellulose. I am sealing all joints and penetrations with caulk and spray foam, and will doing R-38 in the vented attic.

    I am concerned about the open space between joists between the upper and lower floors. I want to know if I should seal off this space so that the hot attic air does not infiltrate between the floors.

    In Green building techniques | Asked By Dustin Gohmert | Apr 23 13
    1 Answer

    Spray foam and HRV system questions

    Hi I have a raised ranch.
    I am gutting the first floor and adding a 2nd story addition. With full attic.
    I am going to use open cell spray foam.
    All walls and attic roof lines. After the addition I will use it to finish the basement.
    I am running a 90+ efficient furnace for the 1st floor and basement.
    Which does draw fresh air into it
    I am planning to get a similar unit for the addition
    3 baths with fans, 1 600 CFM range hood
    Would I need to install a HVR unit?
    I live in the Midwest. I heard stories about windows icing up and having to open windows.

    In Mechanicals | Asked By Brian Pasold | Apr 23 13
    3 Answers

    Split heat-pump water heater?

    What's up with that ?
    Are we again left in the dark zone or what ?

    I've easily found a few hundreds of chinese units of split ait to water HP heater,
    a euro Fujitsu model, some asian Toshiba models and a few DE and CH brands doing different designs ...

    Am i missing something here ?
    As far as i know, none of those are available in USA/CA
    and they SHOULD BE.

    anyone found a supplier in North America ??

    i'd settle for anything better than our regular tanks ..

    In General questions | Asked By Jin Kazama | Apr 23 13
    18 Answers

    Closed-cell spray foam insulation - is it safe?

    We are reading lots of things about spray foam insulation, and have just had the attic space in our new home spray foamed with a closed cell variety. We are contemplating fiberglass batting in the rest of the house after reading that the offgasses from this spray foam installation can cause respiratory irritation, even after the initial 72 hours, particularly for those already suffering with asthma. The American Lung Asssociation recommends spray foam insulation. The EPA cautions about the respiratory irritation. What to do? Is this a safe product for home application?

    In Green products and materials | Asked By Caroline Ferguson | Apr 21 13
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