Ventilation, Ventilation, Ventilation…
We are building a net-zero home in Ontario, Canada with air tightness goal of 1-1.5 ACH50. Climate zone would be similar to 5A. We have cold dry winters and hot humid summers. We are building a 2100 sq/ft bungalow with 3 bedrooms and 2 bathrooms on the main floor, with a 2100sq/ft walkout basement. We do not intend on finishing the basement within the next 5 years; however we will have a roughed in bathroom and wetbar area. Ultimately, the basement could be fabricated as a in-law suite in the future.
We have been working with an Energy Consultant who has recommeneded an whole house ERV with an ECM motor. We have been put in contact with an HVAC Designer. The HVAC designer is recommending a simplified connection from the ERV to the air handler to handle the distribution of fresh air with supplemental bathroom fans. He is claiming that an HRV/ERV will not be able to handle to moisture loads in the bathrooms.
I have spent some time looking into and researching these systems. I understand that this question has been brought up in the past, it looks like a while ago now, and systems and methods we use change a lot over time, so I thought I would post my dilemma for some feedback/advice. I have read through previous articles, but did not find advice to my specific questions.
My plan or idea is going against the grain with both the Energy Consultant (who we have not discussed this with) and the HVAC Designer. Hense, my dilemma. I am not a professional in this field, but I am not convinced what is being suggested is the best solution. We would like install a whole house balanced HRV (Venmar E15 or VanEE equivalent) with a humidifier to the air handler. Fresh air would be supplied to bedrooms, great room and rec room while stale air would be pulled from the Laundry room, bathrooms, kitchen (not for the range hood). Our preference is to utilize an HRV instead of an ERV in an attempt not to introduce or hold onto any unnecessary moisture within the envelope during high humidity events, or from humid air from the bathrooms. We would lean on a properly sized ASHP to draw out access humidity/moisture during the summer months (supplemented by a dehumidifier if nesscessary) the humidifier during the dry winter months.
We do not want to install bath fans in the upstairs bathrooms as it seems redundant to add additional penetrations in the envelope, if it isn’t needed. Additionally, unless dedicated make-up air was provided for each exhaust fan. It would seem that every time a bath fans is ran, we would at be temporarily unbalancing the system. The same goes for the kitchen rangehood. We would be willing to add a bath fan in the downstairs bathroom due to he frequency that it will be used (not often, and not for many years.) I also know that occupant behaviours are impossible to predict. We will be installing a kitchen rangehood with less than 350CFM and a condensing dryer.
With that being said, here are my questions below:
Has anyone had a similar setup to what I am suggesting, and do you have any concerns or issues with your system?
Am I overthinking this situation. I do tend to overthink things; however, I like to ensure things make sense.
Aside from contacting the suppliers to confirm the HRV can be the only source of moisture removal, have you had success with setting up only an HRV with a boost mode in the bathroom to deal with the excess moisture?
Does temporarily unbalancing (depressurizing) the system with either a bathroom fan or a rangehood have a large negative impact, or is the amount negligible and not worth worrying about?
If we eliminate the bathroom fans from the equation, would the rangehood still require make-up air?
If providing make-up air for the rangehood is necessary, what would be your thoughts on running a loop of duct into the house and then back to the stove. My thoughts on this would be that if the pipe was uninsulated, it would have an opportunity to temper the air to match the indoor conditions before injecting it around the rangehood. I’m thinking of those days that will be -20 or +40.
I am unable to find much information on a Simplified connection between the HRV and the Air Handler as the HVAC designer is suggesting. He says that what 90% their designs call for. In my eyes, this system would be highly dependant on the air handler running to distribute fresh air. And with all the losses/mixture of air, it would be almost impossible to verify how the air is being distributed properly. Is this a bad idea, or is it more common than I know?
Thank you for your time and advice, all comments are welcomed and will be much appreciated. Please remember, I am not an expert and I am not claiming to be.
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