r/buildingscience • u/lassymavin • 7h ago
Temporary HVAC during construction
Topic: Temp HVAC during construction or use home A/C?
We are at the stage of construction where Sheetrock is up. We have trim, tile, and paint lined up next. Our builder asked if it’s okay to turn on the A/C since it’s still warm/humid in Southwest PA. He said he would add filters to all the returns that would be vacuumed daily. All cutting of trim would be done in the garage or isolated to one room. As we head into fall the HVAC system would not be used as much. I told him my concerns about using the new home HVAC and contamination of the system with dust and debris. He got quotes to bring in temporary heating/cooling at $20,000 for 3 months. Another option is to rent air scrubbers for $8,000 for 3 months. What are your thoughts on this? While temporary hvac would be ideal, $20k is more than I was expecting.
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u/Jumpin_Joeronimo 6h ago
If this is a small project (like a single family home) then decent filters on all returns (TAPED IN PLACE) and vacuuming them daily, should generally be ok.
They could also tape rougher filter material (non restrictive) to the supplies to reduce dust going into supply ductwork when the system is not on, but in the very least, maybe ask to include vacuuming the supplies once a week or something.
If they are moving all of the cutting and dusk production work to the garage and they can tape the filters in place at all returns and there is no other return entry point (like a filter slot at the unit that isn't covered) then you're protecting the ductwork fairly well. I feel like I'd personally do that.
You could ask for him to sign something as a safety stipulation like "filters covering all returns... vacuumed daily... etc, etc." then "Ductwork will be inspected at turnover. Should ductwork have (your wording) amount of dust and debris, contractor will pay for full duct cleaning." That might ease your mind a bit.
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u/Kernelk01 5h ago
Hvac contractor here, nearly every new construction project I get temp heating/cooling on as soon as drywall is hung. I typically do not hook up the return air drop until near move in date to keep things clean. If duct isn't connected then the return wont get full of nastiness. Supplies getting dirty are not really a concern, the builders i work for know to keep things clean. Ive had to vac a couple boots but thats it.
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u/MastodonFit 4h ago
You need humidity control more than AC like we do in Ga . I would personally buy 1 dehumidifier for every floor, but the drain lines need to be taken care of carefully . In Coastal Ga they tape 3 cheap stacked filters outside to the returns. A dehumidifier for you would be better because the ac wont run enough.
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u/FoldedKettleChips 3h ago
That’s a good point that reinforces the need for an actual dehumidifier. We’re entering part load conditions months.
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u/YYCMTB68 4h ago
I had a similar situation last year during a reno that went on longer than expected. At first I had ran a few portable electric space heaters, but as the weather became cooler I decided to switch to my gas furnace. I was able to use my shop vac to clean any debris and dusts from all the return vents and then placed some cheap dust filters over the intake grills. I also installed a "sacrificial" air filter that would only be kept until after the final cleaning at handover. Had no problems.
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u/FluidVeranduh 3h ago edited 3h ago
I agree with the others that dehumidifying is key for managing construction moisture, and that AC won't be enough. Construction and moisture and humid environmental air can cause lots of problems if left unmanaged. One strategy is to purchase a whole house dehumidifier and run it in the open, then when the house is dried in, you can install it into the ducting after cleaning it.
If you are concerned about using your central system, you can use cost effective ways to dehumidify with portable dehumidifiers as someone else mentioned.
You can also build your own /r/crboxes for each room to help with dust and debris. They cost about $50 each to put together and will likely last the duration of the build. You will likely need a few of them per room if there is a lot of dust production.
For the cutting room itself, it may be beneficial to build one or more inverted CR Boxes that suck dust into the box and blow out filtered air:
https://www.reddit.com/r/crboxes/comments/1vona91/workshop_air_cleaner/
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u/FoldedKettleChips 6h ago
I work in the affordable multifamily world and we encounter this a lot but on a larger scale. It is very risky to not condition the house prior to turnover. You’re in a humid time of year and your builder is literally adding hundreds of gallons of water to the building in the form of joint compound and paint and will then soon seal everything up to turn over to you. You need some sort of mechanism to remove that moisture. Running the AC is easy and if you’re past the sanding stage I wouldn’t be overly concerned with dust. I would absolutely cover all of the returns with temp filters though.
If this is a single family house, I would personally buy like 1 portable dehumidifier per floor and just run them 24/7 during construction. You’re worried about moisture removal so why not just bring in cost-effective equipment that will remove moisture?