Mother-in-law Suite Control
I'm looking into some options to provide some HVAC control to my MIL suite tied into my central HVAC. We use the suite as an AirBnB, and I'd like to offer my guests some way to control the temps while they are there and not cool the space when they aren't. A little about my home, my home is approximately 2900 sqft with the suite being approximately 700 sqft of that. I have an Ecobee thermostat that we use to control the HVAC. I currently have sensors in the main living room/kitchen area, primary bedroom, daughters bedroom, suite living area, and suite bedroom. This does a great job of making sure every place is evenly cooled or heated. There are filtered returns in the primary bedroom, main hallway, and suite living room
What I would like to do is place a puck in the suite living area and leave the ecobee sensor in the suite bedroom, put that ecobee sensor in my office, replace the 4 vents in that area with Flairs, and replace the additional 9 vents in my home (ignoring the two bathrooms). I think this would give me the best control between the two sides of the home. I like my temps in the mid 70's and I've had some guest request as low as 68, which I find ridiculous, but try to accommodate in an effort to be a good host even if we are shivering and killing our wallets with electricity costs. With this setup, I feel like if a guest wants its warmer or cooler than the rest of the house they can call for that. If they want it cooler they can lower the temp and the vents in the main part of the house will close and cool down that smaller space much quicker while keep us comfortable over here. If they want it warmer, those vents will close while the AC runs on this side of the house.
I had talked with an HVAC friend of mine that said a system could be put in place with an inline duct valve to the vents in the suite, and an updated board on the HVAC unit and new wiring for a thermostat in the suite, but it would cost more than $5000. I think this would be a cheaper route as I can install it myself and I enjoy smart home stuff.
So from the community, does this sound like a reasonable option? Is there anything I'm missing?
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Official comment
Hi Daniel Todd, Chuck Askew,
It sounds like Chuck gave you some good feedback. Yes, any non-Flair vents are assumed to be open as Flair calculated how many vents it will allow to close. If you specify 15 total vents Flair will close up to 5 Smart Vents at any one time.
If you have any other specific questions or want to discuss this further please reach out to our technical support team - support@flair.co
Regards,
The Flair Team
Comment actions -
First, it's isn't clear to me whether you plan to switch out the other 9 vents with flair vents, or replacing them with something else. For the sake of my opinion/answer, I will assume you would replace all 9 with flair, in addition to the 4 suite vents.
Now... What I have found in my home with about twice as many vents as yours is that the ability to maintain precise differentials of temperature across the house is really difficult, if not impossible. We do prefer a cool 67-68 degree sleeping temperature, but have not been able to get that in our bedroom without also cooling down other parts of the house unnecessarily. Our system ducts have a large amount of leakage, but I believe the primary reason for the difficulty is because Flair will only close 1/3 of the total vents in the system, in order to not cause back pressure problems in your HVAC system. So even though we would like to only have our bedroom at 68 and not waste any energy to cool anywhere else in the house overnight, the system won't let me. It's a good thing it won't because too much back pressure in in the system will cause big problems.
In your case, you would install the 13 flair vents, then set the total number of vents in your system to 15, which includes the 2 bathrooms, which you should leave open. The Flair software will assume those bathroom vents are open (can someone from flair confirm this?) for the purposes of determining how many vents to leave open to maintain 1/3 ope. So Flair will always maintain 10 of your 15 vents open when they system is running. Since the 2 bath vents are always open, then at least 8 of your 13 flair vents would be open at any given time
In the summer, when your system is cooling, if you have guests that set a lower temp than you prefer, then those 4 vents in the suite will likely stay open, and 4 in the rest of the house will also be opened. If there is a part of the house you definitely don't want cooled down to 68 (for example your bedroom), then you should make sure that part of the house has a setting well above the part you are willing to allow to be cooler.I suppose you could manipulate Flair by telling it you have a different number of vents than you actually do, but then you are gambling with back pressure problems.
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Awesome response, Chuck. I haven't yet looked at the Flair app to see the setup or anything. There are four vents that wouldn't be "Flaired", the three bathrooms (2 main and 1 suite) and the laundry room (main). I have an 8x8 duct in the kitchen I could also leave open as it's on the south side of the house and gets pretty warm during the day. I figure that would help with the back pressure issue a bit. My home is only a year old, and to my knowledge doesn't have any duct leakage issues. I don't mind being a little cooler on this side of the house to be honest, my wife doesn't enjoy it. If only a few vents on this side were left open to rapidly cool the smaller space down, that would be okay. With the system designed to cool such a large space only having to worry about cooling a third of it down, I imagine it would do so pretty quickly with 30% of the vents closed. Honestly, it's mostly about guests feeling like they have control over the temps in the space while they are there. I can justify the cost as a business expense, but I'd like to avoid the high cost of the in attic solution if possible. This may work for me. My ecobee setup and HVAC system already do a pretty good job of equalizing temps across the house as is.
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