Townhouse Retrofit Ventilation
On the same TH project I asked about today. I am trying out a couple of scenarios for ventilation too. Ever since reading John Semmelhack’s report on the cost effectiveness of HRV/ERVs I’ve been wanting to try out exhaust only ventilation systems.
I think the set up can be relatively simple. Replacing existing bath fans with Panasonic FV-08VKS3 (80 cfm) or FV-08VK3 (50CFM). Since this house will end up being relatively tight, we’ll need replacement air. I am thinking about putting FV-GKF32S1 in each of the bedrooms.
Here are some questions:
1. Does Panasonic FV-08VKS3 provide constant ventilation? Or is it intermittent like other bath fans? Couldn’t get a clear answer on Panasonic’s site.
2. It looks like the passive vent FV-GKF32S1 has three settings cCosed, 12 CFM and 18 CFM. Looks like I might not be able to achieve balanced ventilation with this unless I get more passive vents?
What do you all think?
I am worried about my heating load. At the Arlington Passive House, all winter, the indoor temperature stayed above 70F with the minisplit kicking-in very occasionally. A few weeks ago, I went over and cleaned the filters to the ERV, I must have installed one of the pie shaped filters incorrectly and caused the desiccant wheel to stop spinning. So, the ERV was blowing 154 CFM of outside air into the house without heat exchange. This caused the temperature to drop very quickly. Because the MiniSplit heating capacity was designed with the ERV in mind and it was unducted, the result was that it was difficult for the MiniSplit to keep up with the 32 degree air outside.
I suppose the answer is to up-size the heating system if the exhaust only system is constant venting. Thanks in advance.
Roger
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Replies
Roger,
Q. "Does Panasonic FV-08VKS3 provide constant ventilation? Or is it intermittent like other bath fans?"
A. Most bath fans are controlled by a wall switch. They run continuously when the switch is turned on; they don't run at all when the switch is turned off.
The Panasonic FV-08VKS3 is different. Here is the explanation from the Panasonic website:
"This fan is equipped with a CustomVent Variable Speed Control. This allows the fan to run continuously at a pre-set lower level of 0, 30-70 CFM that can then be elevated to a maximum of 80 CFM when the switch is turned on. A High/Low delay timer (adjustable up to 60 minutes), will then return the fan to the minimum CFM level after a period of time set by the user."
For more information on passive air inlets, see Designing a Good Ventilation System.
Martin,
Thanks for your response. I have some follow-up questions. In the post you directed me to, you stated, "If you do install an exhaust-only ventilation system, don’t bother installing passive fresh air inlets in the walls. Fresh air will find its way into the home through random cracks." But my assumption is that this is going to be a pretty tight building (1ach50 or so).
Are you saying I shouldn't build tight?
Thanks
Roger