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Radiant to make downstairs warmer?

baltik | Posted in General Questions on

We live in a mild climate in SF Bay area in a cool/foggy zone.

House is late 60s build and we’ve replaced the single pane windows but the original insulation, 2×4 construction and high ceilings make for a pretty inefficient home.

Heat is currently supplied with a mr cool universal heat pump (5ton) it works well for our needs but not surprisingly there is a meaningful temperature imbalance. It will be 67 downstairs in the family room but 73 in the upstairs bedrooms. (There is no way to close off one floor from another)

House is 3100 sq feet and we are planning on adding another 5-600 feet downstairs. (1000-1200 total downstairs)

One option we could do is to add radiant downstairs (staple up w/ plates in existing area and slab for the addition). We already have a navien NPE 240 and could add radiant relatively affordably. My concern is – if we turn down the forced air to bedrooms to say 65 at night, would the radiant essentially run all night as all the heat would escape upstairs? Would i be better off just creating a separate forced air zone for downstairs?

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Replies

  1. BirchwoodBill | | #1

    It all depends on you you zone your floors and run the tubing. For instance, my radiant heat comes from my hot water tank/boiler through a heat exchanger which lowers the water to under 100F.

    If you place a thermostat in a zone, it will only open the valve (heat) when needed and heat the zone. For our open floor plan, we keep the floors in the bathroom at 72F and the heat in the bedrooms at 68F. Bathroom floors are warm, bedrooms are cool.

    A good radiant designer can help. Have you contacted Hydronica? They are a local bay area company.

  2. user-6623302 | | #2

    You are suffering from stack effect. Warm air is rising and leaking out the top of the building. Cold outside air is entering at the bottom to replace the warm air. You need aggressive air sealing. I do not think additional heat sources will solve the problem and it may make it worse.

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