[Greenbuilding] Buildtight Ventilate right

[John Straube]

Once you have an airtight house and quality (read efficient) ventilation system, natural ventilation does not really save a worthwhile amount of energy in houses but causes all kinds of challenges for construction design and operation while remaining unreliable.
In large buildings, natural ventilation may be worth the effort, but in a typical SFH, hardly.

Stephen Collette wrote:
> Nick,
> 
> Thank you, as you are absolutely correct. The concept of Energuide 80  
> or HERS 20 is for solar ELECTRICITY for payback to be worthwhile.
> 
> I agree with you a bazillion percent that solar air heating is the  
> most viable, and completely ignored side of solar that has something  
> like a couple of hours for payback. ;-)  I think all new buildings  
> should have some form of solar air heating. It's stupid not to. Period.
> 
> As for mechanical ventilation, yes you are right. (fabulous  
> calculations back and forth from units by the way) Once we get tight,  
> we need to ventilate right. That sucks.  I'm interested in others  
> thoughts on natural ventilation ideas actually.
> 
> Thanks for keeping me in line.
> 
> Stephen
> 
> Stephen Collette BBEC, LEED AP
> Principal
> Your Healthy House - Indoor Environmental Testing & Building Consulting
> www.yourhealthyhouse.ca
> stephen at yourhealthyhouse.ca
> 705.652.5159
> 
>> "Solar" as in solar electricity?
>>
>> IIRC, an average US house is 2400 ft^2 and leaks about 0.7 ACH, ie
>> 0.7x2400x8/60 = 224 cfm, enough fresh air for 30 half-time occupants,
>> and a Canadian house that just meets the IDEAs standard leaks 0.15
>> m^3/m^2-hour with a 50 Pa blower door test. Assuming that's wall+floor
>> m^2, a 2400 ft^2 IDEAs house with 369 m^2 of envelope surface would  
>> leak
>> 55 m^3/h at 50 Pa, or 55/20/60 = 0.046 m^3/min, ie 1.7 cfm. So it  
>> needs
>> a mechanical ventiation system for fresh air, esp on warm calm days,  
>> eg
>> an exhaust fan.
>>
>>> I'd have to agree with that having done some energy modelling on the
>>> HOT 2000 program, that we use up here. So it's envelope efficiency,
>>> energy efficiency, lifestyle efficiency, then solar panels. It's not
>>> glamourous, and that sucks, but as we all know, this is what we have
>>> to try to sell to our clients.
>> Solar air heaters can be 100 times less expensive per peak watt than
>> "solar panels," and houses in cold climates need about 5 times more  
>> heat
>> energy than electrical energy, or maybe 10 times, with CFs and  
>> efficient
>> appliances.
>>
>> Nick
> 
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-- 
Dr John Straube, P.Eng.
Associate Professor
Dept of Civil Engineering & School of Architecture
University of Waterloo
Waterloo, ON Canada