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Direct Vent Furnace for Basement

Posted by cuprous (My Page) on
Wed, May 14, 14 at 16:33

I am in the planning stages for a basement remodel and have been having a difficult time settling on the heat solution.

The finished space will be approximately 700 sq.ft. all open no rooms, all below grade. Climate mid-New England. During this past, cold winter the temperature in the basement never got below 50 oF. I would be looking to increase to 68-70 oF.

I was considering a Rinnai ES38 (38k BTU) direct vent wall furnace to heat the space. I had installer come out to provide an estimate and he says I need ~40-42k BTU to heat the area and the Rinnai unit is too small. I did a rough heat loss calc. and come up with 20-22k BTUs. Does this sound more reasonable? Would this actually be a viable option?

He is proposing add additional supply lines off the main trunk from my forced hot air furnace. I like the idea of using the existing heat source but do not want to risk altering the comfort level of the 1st floor and have heard horror stories about poor zoning of existing furnaces. I pushed back on this idea.

A second installer wants to put in a separate furnace 40k BTU 95% forced hot air with a 1.5T air conditioner. I think this will be too big for the space and a mistake.

Any suggestions or are my assumptions on the options above incorrect?

Follow-Up Postings:

RE: Direct Vent Furnace for Basement

Why do they suggest the a/c? My basement here in NJ never went above 68 during this past scorching summer. There was one month of high humidity, but a dehumidifier would have done that job.

RE: Direct Vent Furnace for Basement

I represented Rinnai in its largest US heating market, New England, for 20 yrs. I've trained thousands of dealers/techs on install & service on the Energysaver units. As well, I sold over 180,000 units. Since '91 when they were introduced I've heated my homes, garage and basement with them. Your heating contractor is wrong. It is an outstanding unit for basements.

One of the things I like the best about the basement applications is that you are separating the upstairs heating from the basement. I would not want to be tying the basement air to be drawn and mixed into the air going to my girls rooms. I just don't think it is a good idea. Radon and/or possible negative pressure issues in the basement is just not good to pump basement air into the house.

Unless you have a walk out basement with exterior walls exposed down to the footing I strongly question being over 40kbtu in 700 sq ft. Personally, in a normal basement ( sub-grade) for 700 sq ft I'd select the EX22. I heated 750 sq ft in my first floor in MA with a 22 very very comfortably. It was an open floor but the 22 did a great job. The 38 will certainly do the job, but it will almost certainly be oversized...substantially. Heat loss is based up delta T, difference in temperature. You will have some of the wall against outside air temps, but as you get to ground level and below the delta T is reduced and therefore so is the heat loss. Again, I have probably 10-15,000 units in the field in basements and I took trouble calls gladly...because there were so few. It is a great product and you will be very comfortable with the 22 or the 38.

Oh, and one of the things I liked about the Rinnai in the basement was that after I ran it for a while it would heat the basement ceiling/first floor. It acted like a radiant heater for that floor. It changed the comfort characteristic of the first floor area. Happy Heating!

RE: Direct Vent Furnace for Basement


Thanks for your input which is what I was expecting to hear all along. I will contact a few additional authorized Rinnai installers and move in that direction.

I have received one quote already. Does $2800 sound reasonable for the EX38 installed?

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