[Greenbuilding] first certified Passive House in Canada

[Ross Elliott]

All excellent points, John. 

 

Concerning difficulty in air sealing to this level, I saw some great
examples of using the structural sheathing layer as the air barrier when I
was at the PH conference in Portland, OR this year, sure seems to be a
better way than poly and tape and acoustic sealant for getting 3X tighter
than R-2000. Freaks out some building officials though.

 

I should clarify my issues with HOT2K to say the problem is really the
EnerGuide Rating System, which is something NRCan is well aware of and in
the process of changing. You might find that despite your best efforts it's
pretty hard to get to an 88, but if you manage that extraordinary feat I bet
you'll never get to an 89 without a heat pump (and what do these rating
numbers really mean?). HOT2K is actually a pretty good modeling tool,
particularly in General mode when you can over-ride the program-specific
defaults and assumptions.

 

Thanks for the great debate, I think we can both agree whatever gets more
really efficient homes on the ground is a good thing.

 

Ross Elliott

 

 

From: jfstraube [mailto:jfstraube at gmail.com] 
Sent: Tuesday, January 25, 2011 10:27 PM
To: relliott at homesol.ca
Cc: 'Green Building'
Subject: Re: [Greenbuilding] first certified Passive House in Canada

 

I like 0.6 at 50 too, but it takes a lot of effort to achieve, and this may not
always be justified.  If I can get it, in cold Canada, I will take it every
time. But if I only get to 0.9, then the house can still use the same energy
as a PH with some other modifications.

 

I also hear that the reason for the 0.6 is to limit condensation (would it
not be nice to have this documented somewhere other than in interviews with
Herr Feist?).  

However, if I design a wall properly, say placing half the insulation value
outside of the wood framing, and use a ventilated space behind the cladding,
it is essentially impossible to get condensation, even with, say, 2 ACH at 50.
So if condensation control is the goal, we have the science and experience
to support alternate methods of achieving that goal.  The frost balls on the
outside are not harming anything and we have many years of experience to
show that R2000 airtightness has licked the condensation problems in
climates much more severe than Germany.

 

If energy saving is the issue of air tightness, then trade-offs between
other components of the building should be allowed: it should be rolled into
the energy target.  There needs to be a limit to avoid comfort problems and
IAQ problems: likely this is in the 1.5 to 2.5 range depending on climate.
But the energy and condensation reasons are not technically supportable.

R-2000 air leakage limit is 1.5 at 50.  Thousands have been built.    We can do
it.  Thousands of homes have been built to 0.6.  We can do this.  The
question is, how much work and how worth it is it?  

 

This is the type of conversation that is needed.  0.0 ACH at 50 is nice and
good, 0.5 is better than 0.6.  Why 0.6 and not 0.7 or 1.0.  If people are to
follow the standard, there should be a good reason for the number or it
should not be a hard requirement.

 

Can you point me to more information on how HOT2K does not handle high
performance homes? It was developed based on careful comparisons with real
houses in the Canadian climate with Canadian occupants, and has worked well
in my experience.  I would like to see more of the problems you or others
hace identified (and I bet NRCan would like to have some real info on this
too) since I dont know of them.  Many are using HOT3000 to get more accurate
solar DHW and thermal mass feedback, although I would use WUFI PLUS (a
German program with very good detail) to truly capture thermal mass.   My
retrofit house has an ERS rating of 86, which I achieved without a ground
source heat pump, and with some changes I made this last year, I bet I would
get 88 now.

 

I like the open-source PHPP, but to make it this open they made a lot of
simplifications and assumptions that limit its accuracy.  It is fine in my
books (I have my own set of spreadsheets I use, but they are based on hourly
weather data, not monthly), but it is not correct to say it is more
sophisticated, or more accurate, or more advanced (I have all claimed) than
many other programs out there being used to design high performance houses.
Check out the CEPHEUS 100 house study: predictions varied around measured by
+/-50% like most prediction programs.

 

The Net Zero homes should not use "exorbitantly expensive renewable energy
systems" to reach zero.  Please look into them in some more detail.  For
example, some of them have R100 roofs and R70 walls and ACH around 0.5.
They compared the cost of insulation or the cost of heat pumps or the cost
of renewable energy systems and tried to choose the least cost path to
optimization.  Adding R20 of foam to an R20 foam slab (which seems common to
some PH designs) is more expensive than using PV at market prices to save
the same amount of energy that could be generated by the PV.  Adding $10000
of insulation to say $250   PV can be wastefully deployed.  Insulation and
airtigtness and windows can be wastefully deployed.  Todays PV systems will
likely have the same lifespan or more than the glazing in the windows so I
dont get the "obsolete" comment.

  

 I dont think PH's sole emphasis on insulation and airtightness is
necessarily the right philosophy: nor do I believe Net Zero is the best way.
I am sure that PH is not perfect and should be open to explaining its
reasoning better than it does, and be more flexible to local climate and
practise.    You, Ross, are one of the level headed PH advocates who is
willing to admit "PH is not the answer to everything", which makes this an
enjoyable exchange.

 

John

 

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