Basement Heatloss - Boston
Curious if I'm overthinking my heating need for my basement renovation. 115' perimeter, 50% above grade, all walls R15 closed cell, 7' ceilings with new 4" poured slab, 85sf of replacement R3 windows and a door. We run a 125k steam boiler with insulated pipes, that certainly throws off some heat. Call it 75 BTU/degree hour, with a 9F design temp, 4500 BTU/hr not including the boiler gains back of the napkin math? I can add a 7k mini split head on to my multi split compressor pretty easily, but even that seems overkill. The reality is we usually average around 30F in the winter months, so it's probably half that the majority of the year. And I imagine we'll keep the heat 60-65 and just bump it up nights and weekends /as needed.
Right now we've had multiple 100F days and it's 68F and cool, with zero insulation and a couple leaky windows and a door. Can't imagine there is any cooling load. And mini split heads don't dehumidify well if they aren't actively cooling.
Do I need to think about humidity? It'll have a new vapor barrier under the slab. I'm almost thinking just throw heat strips in there with an in-wall dehumidifier instead of the mini split wall head. Any suggestions?
Comments
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Whole house dehumidifier. Smallest single mini is 9000, BTU/h that too large. Maybe a 4 or 5000 window shaker.
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What about something like this?
Would that put off enough heat in the winter?
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a whole house dehumidifier with an outside air hookup to maintain slight positive pressure.
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How humid is the basement? Has it been too humid in the past?
It seems you are asking more about heat for the basement. If so a load calc would show what is required, possibly the piping heat loss covers the load?
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
I'm with @hot_rod on this one. What have been your experiences in the past? say last winter was very cold in January…. That usually happens every year but we can just look at last year. What was the basement temperature for most of the January days?
- Reply A: The basement was the correct temperature. answer: It ain't broke. Don't fix it
- Reply B: the basement was warmer than i would like. Answer: Add some insulation to the pipes
- Reply C: The basement was cooler than I would like. Answer: remove som insulation from the main pipe
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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I don't think it gets below 55-60F in the winter, and it's basically uninsulated at the moment. While now is the time to plan for a mini split when we are framing, honestly it feels like a dehumidifier with a couple heat strips as a backup would cover most days of the year. A 2" steam main puts out 200 BTUs/ft without insulation. There is a bunch of 1.5" runs on the finished side, maybe 45' that will put out a bit less. Feels like that would get enough hit in the room plus a dehumidifier. On the coldest days it'll run 75% of the hour.
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where is the humidity coming from, water in the basement? Or the outdoor humidity leaking in?
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
right now the outside since it’s not insulated yet. No idea what it will be like with new slab/vapor barrier and CC insulation.
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