Squamish BC Infill bldg – Ventillation
Hello All,
My name is Mark Keschbaumer, a residential designer in Squamish, BC, Canada. Long time reader – first time poster. I been designing homes for 25 years, many of which are green / net zero type projects.
I am about to start construction on a personal project and is a bit of a unicorn. In 2005 I designed and built a 4700sf wood frame mixed use building in downtown area of Squamish, BC that contains 3 residential apartments atop 3 small commercial units that are all operated as rental units.
I have now designed an infill building to be located at the rear of the property and will contain 2 dwelling units – a 700sf 1 bedroom unit and a 1300sf 2 level unit above. The 1st storey at grade is open air parking with a small ‘work’ space that will service as entry and access to an elevator to the 3rd floor.
We need to meet Step 4 of the BC building code (which goes from 1-5 with 5 being net zero). My Energy report calls for mini-splits and HRV’s and we are not allowed natural gas.
The building will have a decent envelope (r24 batts + 2″ mineral wool outsulation) and am hoping for air-leakage ACH 1-1.5 max. Squamish has a relatively warm climate for Canada (marine coastal). I will use mini-splits but I am questioning the need for an HRV. I would like a simple exhaust only bath fan with passive inlets in bedrooms and living area. Building code would permit this so long as our energy report accounts for the less efficient system.
I am aware of the Lunos hrv’s but they are expensive, also a maintenance item and I am concerned with fan noise in bedroom and long term (think 20+ years) reliability of a motor that has to change direction repeatedly.
My question is – are there hidden consequences of bath fan ventillation system aside from the energy penalty I should be aware of? Having been a landlord for 20 years taught me that building systems for rentals need to be as absolutely simple as possible.
Thanks in advance, screen shot of the project attached.
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Replies
Mark,
I'm on the Island, west of Sooke.
Exhaust-only is still the most common choice for smaller dwellings here. The two main downsides are comfort, as the incoming air is not conditioned, and that the residents very often turn the fans off and rely on opening a window when it gets stuffy. Probably not a popular opinion here on GBA, but I'd tend to favour the exhaust only option.
It seems to beg the question of what’s the point of air sealing?
Freyr-design,
At least in theory, the make-up air is supplied by passive vents. How much actually comes from those vents, as opposed to through air-leakage, I don't know.
Mandating full time mechanical ventilation here has been interesting. Unlike the rarified world of GBA building science enthusiasts, it has been greeted with resistance and derision by the wider public, to the point that our code had to require that the controls for the ventilation systems be located in a hard to access place to discourage occupants from turning them off.
Ya it just seems like it would have a larger negative energy effect than just allowing air through entire shell, which begs the question of why air seal at all?
feyr_design,
Don't we air-seal basically for three reasons?
- To reduce heat loss due to air-leakage
- To stop moist interior air from moving through assemblies
- Comfort
I can only see exhaust-only ventilation maybe affecting the latter.
Isn’t it exactly affecting the first one also? You are blowing conditioned air out of your house..
frey-design,
Good point. I was comparing it to balanced ventilation, but yes you lose the advantage of heat recovery without an ERV /HRV. How much that matters in Squamish I don't know. Here on the Island, where my all eclectic house averages out to $7 a day, that's not something I'd worry about
In MN, exhaust only is no longer acceptable, I think. Some townhomes built in the mid 2000's used exhaust only with a continuous running upper level bath fan. The units also did not have exterior foundation insulation with any integrity and those main floor slabs were frigid, as in 55F or so, 10' from the outside wall. I would say the exhaust only ventilation exacerbated the lower level cold floor condition as the stack effect was pronounced by the continuous running fan.
In a mixed climate, exhaust only may be fine, did not work in cold climate Minnesota.
Doug
I've used Panasonic WhisperComfort ERV for venting 2 bed apartments. The unit is a bit more than a regular bath fan but not that much more. You can also cut a 3" hole into one side of it to duct the fresh air supply to the living space/air handler intake.
It is a bit more maintance as you have to clean the intake filter yearly (washable unit so no extra cost). Usually done when replacing the filter for the air handler so not a big job.
Speaking for air handlers, after cleaning the coil on a couple of wall mounts, I've stopped using them. A slim ducted unit is more expensive and definitely more expensive of an install but it takes a proper filter and the only maintaince is swapping a standard furnace filter. Bonus is you can duct it to all your rooms so you don't need aux heating anywhere.
Will see how the units hold up in the long run, they are pretty simple inside (PCS motor with dual blowers on it) and a simple control module. These are wired to run continuously at low speed and there is a motion sensor in the bath to trigger boost, limits any user training or interaction.
Thanks Akos, I was aware (but forgot) of the Whispercomforts but will revisit that if I in fact have to have some sort of mechanical supply
AFAIK (and I don't know much,) the step code still has a massive loophole with respect to natural gas. You just need to tell the energy model that you will buy Renewable Natural Gas when the project is done and presto-bingo, anything goes since the RNG basically shows up as zero carbon.... That said, I'd never want natural gas in a rental building.
Is passive an option in the code in your multi-story building? https://www2.gov.bc.ca/assets/gov/farming-natural-resources-and-industry/construction-industry/building-codes-and-standards/bulletins/b14-05_9_32__ventilation.pdf
Our existing units heat primarily with gas fp and would do same again in a heart beat. Thanks for the link to the pdf - but I suspect it is now outdated with Step code now in effect.
Apologies for being absent - could have swore i turned on notifications but never received any and thank you all for the discussion.
If there is some way I am allowed do passive supply I will. Squamish is relatively warm and energy/operating cost penalty minimal. Our existing units with passive supply function just fine and zero problems or maintenance in 20 years.
My BI they said I cannot because code says if it is a 'Step Code' building - passive supply not allowed. (screenshot attached). I have email the province to ask for clarification because I am not sure I agree.
Intake and exhaust vent locations also a challenge. The infill is shoe-hormed into very tight space on the property and 2 of the 4 exterior walls are non-combustible assemblies and no penetrations permitted.
Using Lunos vents in bedrooms is something I wouldn't recommend. I have that setup!
Even at the lowest speed, they make quite a bit of noise. If you go this route see if it's possible to locate them in a nearby closet to disguise some sound.