sunroom floor

Discussion in 'Alternative Energy' started by Ed Norman, Oct 16, 2006.

  1. Ed Norman

    Ed Norman Well-Known Member

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    We built a sunroom on the front of the house. Luckily, that faces south. It is 9' tall and has 24' wide and has 8mm double wall lexan for glass. On sunny days when it is warm, we'll open the door and a window and let the heat in, maybe use a fan to blow it in. The ceiling is insulated. We're wondering what to put on the floor. We'll shut the door and window in late afternoon, but DW plans to start plants out there next spring. I thought some kind of dark rocks might absorb heat and give it off at night to keep things a little warmer. But would we need insulation under the rocks to keep the ground from sucking all the heat? What kind and how much? And how much rock?

    In the summer, the panels of lexan come off and it becomes a porch.
     
  2. WisJim

    WisJim Well-Known Member Supporter

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    What is the floor now? We did a concrete slab with tile, insulated with styrofoam under the slab.
     

  3. Ed Norman

    Ed Norman Well-Known Member

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    Dirt and grass. A few weeks ago, it was the front lawn.
     
  4. mohillbilly

    mohillbilly Well-Known Member

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    Just an idea here......get some plastic or metel 55 gallon barrels. paint them up a dark color (flat black) and fill them with water (about 4 or 5 of them I am guessing) the heat from the sun during the day will heat the water. at night the thermal mass of the barels will release into the room keeping it warm. would be much more effective than the rock idea in my opinion due to the greater mass and minimal ground contact.
     
  5. WisJim

    WisJim Well-Known Member Supporter

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    If you don't want to pour a slab, I would suggest "patio blocks". Around here, those are 8x16x2 inch (if I remember right) colored concrete blocks for walkways, etc. Some of them in a darker color on a bed of sand would be a fairly level floor with a reasonable mass. And then also try the barrel suggestion--I used to get 15 gallon black closed top barrels from work--they now get cloudy white barrels--and fill them with water and set them where the sun can shine on them and also use them to hold plant trays, etc.

    If you do put in some kind of floor, insulation around the edge would be better than no insulation under it at all.
     
  6. joken

    joken Well-Known Member

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    Ditto the 55 galllon drums
     
  7. fernando

    fernando Well-Known Member

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    There are many ways to accomplish the heat-reservoir capability you seek. However, to my way of thinking, the first thing you must determine is how weather-proof the room will be when you take down the lexan and revert to an open porch.
     
  8. SolarGary

    SolarGary Well-Known Member

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    Hi,
    There is a tradeoff here between getting the most heat for the house from your sunspace, and keeping the sunspace above freezing for plant growing.

    If you want most heat to the house:
    keep the thermal mass in the sunspace down to a minimum. When the sun is on the sunspace, blow the hot air from the sunspace into the house. When the sun is off the sunspace, close the doors between house and sunspace, and let the sunspce get cold. This gives you max heat to the house, because there is no thermal mass in the sunspace to absorb heat and lose it to the outside. In this case the floor should be something that does not absorb heat. I've heard of people using something like garden bark that insulates fairly well.
    This writeup from the Shurcliff book explains this low thermal mass approach pretty well:
    http://www.builditsolar.com/Experimental/ShurcliffPart1/PolySpace.htm

    If you want to raise plants:
    You need to have enough thermal mass in the sunspace to absorb heat during the day, and give it back at night to keep the temp from dropping below freezing. I think all the schemes already mentioned will work. If you use the floor for mass, I think you should insulate under it with rigid foam board insulation. The other insulation approach is to insulate the perimeter with vertical foam board pieces that go down about 2 ft all the way around the edge. Unless you live in a mild climate, this won't be enough to keep the susnpace above freezing all winter. The other thing you need to do is to insulate the windows at night with some form of rollup or removable insulation. If you don't provide the window insulation, the heat loss through the windows is really high, and you will end up needing to use house heat to heat the sunspace to keep it above freezing.

    This approach will result in less heat from the sunspace going to the house, because whatever goes into the sunspace thermal does not make it to the house.

    Some people just don't grow try to grow plants in the coldest months.

    Some sunspace, thermal mass, and insulation schemes here:
    http://www.builditsolar.com/Projects/Sunspace/sunspaces.htm
    The Andrew Shapiro book thats listed at the top is really good for this, and you can find it at the used internet book stores very cheap.

    Gary
     
  9. Al. Countryboy

    Al. Countryboy Well-Known Member

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    We has a sun room that is 16ft.X48ft. which is lenght of our house. It has a concrete floor. We live in the southeast and do not have extreme cold here. On sunny days with temps. in the 40's the temp. in the sun room can be in the 90's. I do feel that we should have insulated under the concrete floor for better results. We have also tried putting a vent into our bath room which was working quite well until we started getting mold around the ceiling. I believe that the air coming into the house has to moisture. There are 4 windows and a French door on the back of the house that sometimes is opened some to let heat into the house and don't seem to have a moisture problem. The vent was at the very top of the sun room into the bath and maybe most of the moisture was in the top of the sun room. We have tried keeping veggies through the winter, but they do not seem to do very well. I feel that the days are to short, but in about Feb. we do start alot of our seeds for the garden which do really good. Our house plants also do quite well in the winter with little or no heat. You might try putting down insulation board and buy those 2ft.square concrete tiles. Many different patterns to chose from if you want to use it like a den on sunny winter days. My sun room is really nice in the winter, but can get really hot during the summer even with all 22 windows and 2 doors open. I hope that you will enjoy yours as much as we have ours over the years.
     
  10. farmergirl

    farmergirl Well-Known Member Supporter

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    We rented a house once that had a simliar set-up and the floor was made of saltillo tile. It's pretty and inexpensive, though it will crack if the foundation material you use is not level or if you drop heavy things on it.
     
  11. Ed Norman

    Ed Norman Well-Known Member

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    Thanks everyone. We still haven't decided, although the barrels will be used, at least when she starts her plants. If the thing does heat up good on sunny days, we will put in a duct to suck hot air from the ceiling, and duct it under the house to vent in the back bedrooms. That will push air out the open front door to be reheated.

    Too many choices. The bark sounds good for more house heat because I think it will get real chilly when the sun goes down at 4. That might be the way we go.