The question is also then, if option #1 is cheaper, is the cost difference large enough to cover the more efficient option #2 when ammortized out over the life of the system? Very curious to hear your builder's response Guy.

I'm in the exact situation but in a planning / design phase. Please let us know what you hear from your builder.

The Passivhaus people design for .3 to.4 air changes per hour in a shell probably tighter than we're talking about here. That 's a big difference. Where does your number come from?

Have you looked into Nilan HRV's? They use a combo HRV-Heat pump to deliver both hot and cold air and take care of the ventilation at the same time. That's what I plan to use on my project.

Take care,
Adi

IIRC, the 0.5 is from ASHRAE and the 1.0 is something I read but do not recall the source.  These are numbers that would apply to a tight building. 


Bruce

Option #1 came out around $10K total with $6400 for full HVAC ducting and $4300 for Lifebreath HRV/furnace plus enhancements to the Nordic GSHP.   Option #2 came in higher due to the cost of the Multi-Aqua units plus insulated PEX and plumber's installation time.  (All prices are CAN$)

So, I've decided to forgo A/C all-together.  Had A/C been really important, I would have been better to stick with a forced air heating system rather than radiant.  Adding an A/C unit to existing forced-air system is much cheaper than having both radiant and forced-air. 

However, given Calgary's climate, I feel I've made the right choice of prioritizing heating (with a comfortable radiant in-floor system) rather than worrying about a small amount of cooling.  We have a very tight envelope, good roof overhangs, and good windows allowing natural breeze at nights which means A/C just isn't needed.