ASHRAE Journal - August 2011 - 15
letters
2 by 4, plus a 0.25 in. top plate are used with blocks every 4 ft for walls parallel to the trusses. Keep the electrician out of the ceiling as much as possible with lights on interior walls and keep ducting inside the building envelope. Put the attic access on the gable end or in the garage. Instead of vapor barrier joints on each side of every wall, there is a single seam in the entire ceiling with 20 ft wide poly. A cold climate bonus is that the house can be buttoned up and the ceiling insulated after ceiling electrical work is done and, with rigid insulation on the outside walls, the building is better insulated than most houses and comfortable for the trades to work in. Everyone wins. The claim that many houses are over ventilated has merit but is compounded by excessive infiltration. Three ach on two levels of 1,500 ft2 is 60 cfm, which is what most houses need to control moisture, subject to occupant load and, of course, on the volume of volatile organic compounds being emitted by building materials and consumer products. Ventilating by infiltration through insulation is an air quality issue and problematic for occupants who have seasonal allergies or chemical sensitivity issues. Of course, the selection of an appropriate standard of air infiltration is climate related but in southern Alberta, tight is right—making small inexpensive heating solutions predictable while advancing the economics of sustainable building. Emile Rocher, P.Eng., Member ASHRAE when I was a much younger man and actually had to work for a living, constructed several houses using the same approach in 1982. Having said that, I do not agree with you that the approach is practical for large production building sites. But that is only a personal opinion. Your opinion is just as valid on this point as mine. Joseph Lstiburek, Ph.D., P.Eng., Fellow ASHRAE
The Author Responds
I apologize for not being as clear about the units in the recent article as I should have been. The 3 air changes per hour value you refer to is not a “real” air change rate but the rate determined at a pressure difference of 50 Pa. The actual value is probably around 20 times less (as a wild guess since there is no good conversion, which was the point of the column) and, therefore, the energy penalty you are justifiably concerned about is significantly less. The other value you cite is missing a decimal; it is 0.3 ach (no Pascals this time). This, of course, makes a huge difference. Finally, the Passivhaus spec is 0.6 ach, but now at 50 Pa. This is ultratight construction by anyone’s standards. I have no problems with your approach to construction. It clearly works. I, myself,
August 2011
www.info.hotims.com/37989-20
ASHRAE Journal
15
ASHRAE Journal - August 2011
Table of Contents for the Digital Edition of ASHRAE Journal - August 2011
ASHRAE Journal - August 2011
Contents
Commentary
Industry News
Letters
Meetings and Shows
Feature Articles
2011–12 Presidential Address: Sustaining ASHRAE Through Leadership
Retrocommissioning Older Buildings
Liquid Refrigerant Pumping in Industrial Refrigeration Systems
Technology Award Case Studies:
Hospital Upgrade: Heat Recovery, Geothermal Save Energy
Cool Weather Savings: Using Hybrid Refrigeration Systems for Chiller Retrofit
Special Section
InfoCenter
Standing Columns
Solar NZEB Project
Emerging Technologies
Special Products
IAQ Applications
Washington Report
People
Products
Classified Advertising
Advertisers Index
ASHRAE Journal - August 2011 - Intro
ASHRAE Journal - August 2011 - ASHRAE Journal - August 2011
ASHRAE Journal - August 2011 - Cover2
ASHRAE Journal - August 2011 - 1
ASHRAE Journal - August 2011 - 2
ASHRAE Journal - August 2011 - Contents
ASHRAE Journal - August 2011 - Commentary
ASHRAE Journal - August 2011 - 5
ASHRAE Journal - August 2011 - Industry News
ASHRAE Journal - August 2011 - 7
ASHRAE Journal - August 2011 - 8
ASHRAE Journal - August 2011 - 9
ASHRAE Journal - August 2011 - Letters
ASHRAE Journal - August 2011 - 11
ASHRAE Journal - August 2011 - 12
ASHRAE Journal - August 2011 - 13
ASHRAE Journal - August 2011 - 14
ASHRAE Journal - August 2011 - 15
ASHRAE Journal - August 2011 - Meetings and Shows
ASHRAE Journal - August 2011 - 17
ASHRAE Journal - August 2011 - 2011–12 Presidential Address: Sustaining ASHRAE Through Leadership
ASHRAE Journal - August 2011 - 19
ASHRAE Journal - August 2011 - 20
ASHRAE Journal - August 2011 - 21
ASHRAE Journal - August 2011 - 22
ASHRAE Journal - August 2011 - 23
ASHRAE Journal - August 2011 - 24
ASHRAE Journal - August 2011 - 25
ASHRAE Journal - August 2011 - Retrocommissioning Older Buildings
ASHRAE Journal - August 2011 - 27
ASHRAE Journal - August 2011 - 28
ASHRAE Journal - August 2011 - 29
ASHRAE Journal - August 2011 - 30
ASHRAE Journal - August 2011 - 31
ASHRAE Journal - August 2011 - 32
ASHRAE Journal - August 2011 - 33
ASHRAE Journal - August 2011 - 34
ASHRAE Journal - August 2011 - 35
ASHRAE Journal - August 2011 - Liquid Refrigerant Pumping in Industrial Refrigeration Systems
ASHRAE Journal - August 2011 - 37
ASHRAE Journal - August 2011 - 38
ASHRAE Journal - August 2011 - 39
ASHRAE Journal - August 2011 - 40
ASHRAE Journal - August 2011 - 41
ASHRAE Journal - August 2011 - 42
ASHRAE Journal - August 2011 - 43
ASHRAE Journal - August 2011 - Hospital Upgrade: Heat Recovery, Geothermal Save Energy
ASHRAE Journal - August 2011 - 45
ASHRAE Journal - August 2011 - 46
ASHRAE Journal - August 2011 - 47
ASHRAE Journal - August 2011 - Cool Weather Savings: Using Hybrid Refrigeration Systems for Chiller Retrofit
ASHRAE Journal - August 2011 - 49
ASHRAE Journal - August 2011 - 50
ASHRAE Journal - August 2011 - 51
ASHRAE Journal - August 2011 - InfoCenter
ASHRAE Journal - August 2011 - 53
ASHRAE Journal - August 2011 - 54
ASHRAE Journal - August 2011 - 55
ASHRAE Journal - August 2011 - 56
ASHRAE Journal - August 2011 - 57
ASHRAE Journal - August 2011 - 58
ASHRAE Journal - August 2011 - 59
ASHRAE Journal - August 2011 - 60
ASHRAE Journal - August 2011 - Solar NZEB Project
ASHRAE Journal - August 2011 - 62
ASHRAE Journal - August 2011 - 63
ASHRAE Journal - August 2011 - 64
ASHRAE Journal - August 2011 - 65
ASHRAE Journal - August 2011 - Emerging Technologies
ASHRAE Journal - August 2011 - 67
ASHRAE Journal - August 2011 - 68
ASHRAE Journal - August 2011 - 69
ASHRAE Journal - August 2011 - 70
ASHRAE Journal - August 2011 - 71
ASHRAE Journal - August 2011 - 72
ASHRAE Journal - August 2011 - 73
ASHRAE Journal - August 2011 - 74
ASHRAE Journal - August 2011 - Special Products
ASHRAE Journal - August 2011 - IAQ Applications
ASHRAE Journal - August 2011 - 77
ASHRAE Journal - August 2011 - 78
ASHRAE Journal - August 2011 - 79
ASHRAE Journal - August 2011 - Washington Report
ASHRAE Journal - August 2011 - 81
ASHRAE Journal - August 2011 - People
ASHRAE Journal - August 2011 - 83
ASHRAE Journal - August 2011 - Products
ASHRAE Journal - August 2011 - 85
ASHRAE Journal - August 2011 - Classified Advertising
ASHRAE Journal - August 2011 - 87
ASHRAE Journal - August 2011 - Advertisers Index
ASHRAE Journal - August 2011 - Cover3
ASHRAE Journal - August 2011 - Cover4
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