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How important is choice of flooring for optimizing solar gain?

Richard Clark | Posted in Energy Efficiency and Durability on

We are building in (I believe it is) zone 6, Cranbrook B.C.
We are working on trying to get the right ratio of floor to window area on the south face. Trying to comprehend the various factors such as amount of direct and indirect sunlight onto the different surfaces and how that effects the ratio.
2 questions.
How important is the choice of flooring? I understand that a dense mass such as 3″ of concrete/tile might be the best choice however the others involved are leaning towards 3/4″ hardwood (Hardwood on conc slab in the walkout bsmnt and on plywood subfloor on 1st floor)

When calculating floor area do we include the rooms separated by walls and doors? (bedrooms and bthrms along the north side) What about a kitchen on the north side open to the south facing main area?

Thanks for info on these questions and any good info on this specific area of design.

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  1. GBA Editor
    Martin Holladay | | #1

    Q. "How important is the choice of flooring?"

    A. You have asked a fairly general question, so I will give you a general answer: not very. Other factors (glazing area, glazing SHGC, overhang depth, envelope tightness, insulation levels) are far more important.

    Q. "When calculating floor area do we include the rooms separated by walls and doors (bedrooms and bathrooms along the north side)?"

    A. For what purpose are you measuring the floor area? I presume you mean for the purpose of calculating the south glazing area, but I'm not sure. These glazing ratios aren't hard and fast, but it's safe to say that you can include the areas of any rooms with doors that are usually left open during the day.

  2. Damon Lane | | #2

    The floor material won't much affect total gain, but if you are at the upper end of glazing ratios, the floor material choice will impact how much the room temperature varies over the day. There is a big difference in the thermal storage capacity of the flooring options you mention.

  3. Richard Clark | | #3

    Thanks Martin and Damon
    Damon used the phrase I was looking for...'Thermal Storage Capacity' (of the floor material)
    We are designing to have a tight envelope, high insul levels, minimal thermal bridging, overhangs designed to shade summer sun, well designed windows(glazing, orientation, SHGC). So now we are considering the 'Thermal Storage Capacity' of the materials used for flooring and for an interior wall that runs along much of the E to W axis 13' in from the S wall. Also trying to calculate the ratio of the South facing windows to the floor area while considering the materials that are recieving the direct and indirect sunlight.
    I am trying to understand these aspects of fine tuning our design after reading of them in 'Green From The Ground Up. (Johnson and Gibson, Taunton Press) and from discussions here on GBA. I am a builder and trying to understand these aspects.

  4. Ray Smith | | #4

    Richard, can you please e-mail me at [email protected]. I am a certified energy advisor living in Creston, and prior to moving to Canada in 2007 I built very energy efficient houses in S. Ireland. I might be able to give you some help based on my own experiences.

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