Adding to existing baseboard heating system
First off, I’d like to say thanks to all the people out there who have contributed to this forum. I’ve learned a lot.
I’m currently working on finishing my basement and I want to add some heat down there. I have leftover Fintube from a recent renovation that I’d like to use, and I think I know what my load is (how much Fintube I’ll need to install), but my concern is with short-cycling my boiler just to raise the temperature about 10 degrees down there.
-Location: Southern Maine along the coast
-Poured concrete walls
-Newly insulated w/ 2″ of XPS, locked in with metal Z-channel 2′ O.C. (drywall will hang on the Z-channel)
-First floor above is 2×10 joist construction–thinking about insulating to cut down on noise
-Buderus G115 (95k btu) oil fired (Riello burner) w/ indirect domestic hot water
-Currently 2 heating zones + the indirect hot water
Last winter, which was relatively mild, my basement temp held at around 60 degrees F without any insulation. The heating pipes are a mix of 3/4″ copper and 5/8″ pex. The pipes aren’t insulated but I’m planning on changing that.
I did a calculation of my heating load based on last winter’s data, as Dana had described in his blog https://www.greenbuildingadvisor.com/article/out-with-the-old-in-with-the-new. I realized that In Jan-Mar I only used about 35K btu of heat from the boiler (the recent installation of a propane fireplace probably offsets about 20-30k BTU of load). Interestingly enough my calcs from Mar-Jun show a use of 45-55k BTU from the boiler. I suspect that the fireplace was used less in those months but I have nothing to back that up. It was a cold rainy spring.
So right off the bat, I know that my boiler is oversized for my current house application. However, I’m planning on finishing a space over the garage (about 700 sq ft) and adding a heating zone there. I also would like supplemental heat in the garage. The space above the garage will likely be insulated with spray foam. So, it seems that I’ll still have more than enough heating capacity for that space.
Back to the basement: Based on a quick calculation at https://loadcalc.net/ I found that my basement will require about 6500 BTU of heat. At 580 BTU/foot, I should only need about 11 feet of Fintube. And that’s for the entirety of the basement…we’re not finishing all corners of it. I’m figuring on putting 3 feet of Fintube under each of the three 31″x12″ windows.
So maybe now you can see where my question is going. With only 9 feet of heat + probably around 90 feet of tubing, I’m feeling like there’s going to be some sort of short cycling involved.
Should I put this on its own circulator pump (currently each zone uses its own 007). Or should I somehow add the basement to the end of an existing loop (like the 1st floor) with a zone valve to allow it on/off whenever it needs heat and the 1st floor is running.
Additionally, about 1/3 of my first floor square footage (15’x25′, 3 exterior walls and one bedroom) is original R11 fiberglass insulation. The rest of the 1st floor got 3″ closed cell when we renovated. This lesser insulated portion is not where the gas fireplace is, and as a result was noticeably colder. So I was considering adding this portion to the end of my basement loop with a 3-way zone valve to add to the run length and provide a bit of “boost.”
Despite all my reading/thinking/etc., I’m unsure what the right/best way to accomplish this is, while using existing parts/systems appropriately/smartly.
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