[GSBN] Straw-Bale Blower Door and Infrared Test Results

[Dan Smith]

Thanks John for your usual thorough insights, I agree 0.6 is unreasonable unless you're dealing with PH certification, getting to 2.4 on the Zeta prefab was a significant effort.  It's good to know that the plaster layers are as effective as a 
membrane barrier.
Dan

...............................
Dan Smith
Principal - DSA Architects
1107 Virginia St.
Berkeley, CA 94702
510.526.1935
Dan at dsaarch.com
www.dsaarch.com

On Dec 24, 2010, at 6:14 AM, John Straube <john at buildingscience.com> wrote:

> Actually Ontario tract homes are closer to 3 ACH on average as of 07 but are likely a touch lower now. 
> However ACH is not a great metric as it makes small houses look worse and houses with basements look better. 
> A better metric is cfm50 per square foot of enclosure area. 
> The total cfm50 number is well under the average Ontario home ( less than half) because this is a small home which means its impact on the world is less than an Ontario home. 
> 
> John Straube
> 519 741 7920
> Sent via BlackBerry
> 
> -----Original Message-----
> From: David Elfstrom <listbox at elfstrom.com>
> Sender: GSBN-bounces at greenbuilder.com
> Date: Fri, 24 Dec 2010 02:11:28 
> To: <GSBN at greenbuilder.com>
> Reply-To: "(private, with public archives) Global Straw Building Network" <GSBN at greenbuilder.com>
> Subject: Re: [GSBN] Straw-Bale Blower Door and Infrared Test Results
> 
> The report says that flow was 617 cfm at 50 Pa depressurization.
> 
> If the house volume is (900 sqft x 10 ft avg wall height) = 9000 cuft ,
> then air changes per hour at 50 Pa depressurization is 617 cfm/9000
> cuft  * 60 min/hr = 4.11 ACH @50 Pa. That is typical for a suburban
> tract home built in Ontario today without any special attention to
> detail, and easily achievable by retrofits.
> 
> Even if the volume were doubled (20 ft average wall height) it still is
> considerably more than new home construction to the R2000 standard from
> the 1990's of 1.50 ACH50. Passive House requires a mere 0.60 ACH50 or less.
> 
> In the report it states "ASHRAE suggest a minimum natural ventilation of
> 950-1200 CFM for a house of this size". I don't think so! That would be
> a seriously leaky house, and would be as dry as a bone in winter. ASHRAE
> actually suggests mechanical ventilation to 7.5 cfm per person + 3 cfm
> /100 sqft, so a four-person 900 sqft home would require a mechanical
> ventilation to achieve a mere 57 cfm for all the fresh air needed.
> 
> David Elfstrom
> 
> On 24/12/2010 12:42 AM, Dan Smith wrote:
>> David and Anni, thanks for sharing this, it is a treat.
>> 
>> What's the air change per hour at 50 Pa?
>> 
>> Happy Holidays,
>> Dan
>> 
>> http://greenbuilder.com/mailman/listinfo/GSBN
>> 
> 
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