Conditioned crawl space HVAC help
I live in british columbia and have a sealed crawl space with a high efficency natural gas furnace and an ICF foundation. The crawl is heated via the furnace. There are some return air grills upstairs that return the upstairs air to the furnace through some floor joists then into the ducting.
The house is only a few years old and the crawl has a smell to it which leeches upstairs. I can only think it is because of the stale air. Would my best option be to install an exhaust fan through the rim joist or is there a better option?
I’m trying to keep the balance with the HVAC system and believe that the exhaust fan will force the air from upstairs through gaps to the crawl space. We also have whisper fans in the bathroom that constantly run.
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Seems like that might work. It would likely negatively pressurize the crawl space forcing the makeup air for the crawl space to either come from outside or upstairs. This may not be the most efficient method.
Another option might be to duct from the crawl space to the bathroom and let that fan exhaust the air from the crawl space. You might need to seal around the bathroom door threshold to make sure the makeup air for that bathroom comes from the crawl space. A disadvantage to this option is that now that bathroom would smell like stale crawl space.
How is the smell leaking up into the house? Through the ducting or through the flooring/structure? What temperature does the crawl space stay at in the winter? Could you close some of the airflow to and from the crawlspace that might lessen the smell or play around with the airflow to see if it has an impact?
Krackadile - we have the upstairs staying at 20 degrees Celsius in the winter which in turn keeps the crawl at 18/19. I did try to seal some of the gapa where wires and plumbing pass through but it didn't help too much. The whisper fans are always running in the bathroom which I believe are drawing up the crawl space air.
Therefore I think a good option would be too have the whispers from not constantly running and to install an exhaust fan in the crawl space for some air flow.
Is it possible that the crawlspace is “conditioned” in name only.
Is the temp and humidity the same as the rest of the house?
Yes, the walls are insulated and air sealed but the space does not have any supply or return vents.
It seems likely the air in the crawlspace has a temp very close to its dewpoint and the surface of the walls sometimes falls below the dewpoint of the air making things get wet and smelly.
Walta
Walta100 - the temp is around 1-2 degrees Celsius colder in the winter and humidity is around the same. 30-40% in the winter and I set the dehumidifier at 60% in the summer but without the dehumidifier it can be at 70%+.
The furnace does supply air into the crawl space and we do have 2 cold air returns in the house that feed the furnace via the thermopan joist liners to the ducting. I guess i coould add a return duct from the crawl space to feed the furnace for airflow. Although in the summer the furnace is off so the air would still be stale.