[Greenbuilding] first certified Passive House in Canada

[jfstraube]

On 2011-01-30, at 3:17 PM, John Daglish wrote:
> Not unexplained if you read German (I dont much) or search out the
> info (google is your friend).  But you know allready.
I do read German, worked in Germany for a year. Reading German does not help explain any of this.
> 
> perhaps this helps
> http://passipedia.passiv.de/passipedia_en/planning/airtight_construction/general_principles/leakage_problems
This is very useful for understanding of anyone following along.  The enclosure assembly shown is just plain old bad building science for a highly insulated assembly. We learned this 25 years ago before I was in the industry.  If you insulate on the exterior, this problem does not happen.  Place, say, half of the insulation level on the exterior as, say, rockwool, and you dont have any problems.
If you dont insulate on the exterior, all 0.6 does is limit the amount of condensation, not avoid it.  Exterior insulation can completely eliminate condensation with 0.75 or 1.25 @50. Nothing special about 0.6
> 
> You can fiddle with the different elements but you may well sacrifice
> human comfort. This is critical to the sucess of the Passivhaus.
I agree you could fiddle too much.  So why not simply state the comfort requirements, say ASHRAE 55, which limits mean radiant temperature, radiation asymetry etc. and then let me fiddle within that range.
>  I repeat in
> the central european climate if you go over 0.3 ACH in a passivhaus you risk
> comfort problems in winter ... too dry air without remedial mesures.

The 0.3ACH natural ventilation is TOO HIGH.  Please read my email carefully as this is what I said.  Lower ventilation rates, based on per person ventilation rates, will lead to higher interior RH.  Sometimes we need to increase ventilation rates in humid maritime climates to reduce RH, we only have problems with low RH in leaky or over ventilated houses.  Seems like the central European experience might apply here, although many times it does not apply.
> 
> j> Another question is, why is it necessary to heat with the ventilation system? This is not a requirement of PH, and many certified PH use heat pumps, pellet stoves, electric heaters etc.
> 
> It is not a requirement but at this rate the HRV can do it if so desired for the
> reasons stated before in a central european climate.
Please read the calculations I presented.  The ventilation air CANNOT heat the air in a cold climate house unless you over ventilate .
The link you provide here
> http://passipedia.passiv.de/passipedia_en/basics/the_passive_house_-_definition
actually completely disagrees with you in bold letters. It says that you must heat the building using ventilation air.  
I quote:
A PH is one "for which thermal comfort (ISO 7730) can be achieved solely by post-heating or post-cooling of the fresh air mass, which is required to achieve sufficient indoor air quality conditions – without the need for additional recirculation of air.”

>  Passing ventilation air through fans and ducts in general is
> not ideal due to contamination, creating and keeping dust suspended,
> creating more positive ions, etc.'
I specifically added an air handler in my recent house after moving from living with radiant and ventilation air only.  Why? Because by not recirculating I did not have the chance to filter the air in the house as well, and recirculation allows you to filter the air.  Once through HRV systems have the real limitation that the dust that comes in on people shoes, clothes and pets cannot be removed.  I have learned that the ultimate, no money spared solution is not an HRV but an HRV with air circulation (my air handler draws 34W to move 300 cfm). The recirc also allows for some heat redistribution from sunny rooms, highly populated rooms, or rooms with equipment suddenly on.  This results in more uniform and comfortable temperature and humidity.

> 
> 
> j> The 10 W/m2 does not work either.
> j> ASHRAE 62.2-2007 is the north american ventilation standard.  It recognizes that both people and houses produce pollutants and hence recommends minimum ventilation of 7.5 cfm/person + 0.01 cfm per
> j> square foot of house area.  This is 50 cfm for a 3 bedroom 2000 sq ft (186 m2) house. PHPP 2007 states that the “average air change rate should not fall below 0.3 ACH.” This ACH based ventilation
> j> is no longer used in North America because research showed it was inadequate: it is the people and the building that need ventilation, not the volume. For a 3-bedroom 2000 square foot single
> j> family home, this results in a PH ventilation rate of 80 cfm versus 50 cfm (25 l/s) for ASHRAE 62.2- 2007.
> 
> j> So if I properly ventilate at 25 l/s, and limit heating to 50 C, then the heating power will be 0.025 m3/s * 1.20 kJ/m3/°C * (50C-20 C) = 900 Watts.  This is 4.8 W/m2 (for the 186 m2 house), not
> j> 10 W/m2.  Of course PH uses different ways of measuring area so maybe it is actually 6.5 W/m2.  In either case, it is only 10 if you over ventilate.  Why build a super tight house with an
> j> efficient HRV and then over ventilate?? This over ventilation is also one reason I think they want such high efficiency expensive HRVs.
> 
> Ventilation per person is probably a better metric but ACH is a
> standard metric often used in housing in Europe. But perhaps our higher rate leads to a
> healthier environment for people considering what off gases/pollutes
> into typical homes? ASHRAE is not God.
Above you say too much ventilation causes dry air.  Here you say it is healthier.  No ASHRAE is not god.  Neither is the Passiv Haus institut. But at least ASHRAE has an open committee, that meets every 6 months, that you or I can (and do) attend to understand the reasons for its values (which 15 years ago where 0.3 ACH, but then the research improved), and it has a completely open and transparent standard setting.  PHI to North Americans is a closed box with gospel handed on down. Even that would not be bad, but the gospel is then told to us is based on superior science. It is this superior science that I am looking for.
> 
> Perhaps this page will end the seemingly inflexibility
> and arbitrariness of the Passivhaus debate :
> http://passipedia.passiv.de/passipedia_en/basics/passive_houses_in_different_climates
I doubt it.  The US Passive House institute is giving courses around the country repeating all of this verbatim from the PassivHaus standard.  Which is why PH US is really PassivHaus.


John Straube
www.BuildingScience.com