Alternative Technology Assn Forums

1. 

   MrEGuy
   Member

   Hello,

   I live in a split level house where the floor on one side of the house has a raised infill slab and I am wondering if there are any smart ways to exploit its thermal mass.

   As it was explained to me the slab that is raised 600mm has fill underneath it as there is no sub floor area and was build way before waffle pads. As the house was built in the early 80s the fill is likely to actually be normal soil, building rubble and trash of some description. I believe the way they made it was to brick up the walls, bring in 600mm of fill and then pour the slab on top.

   Unfortunately there are no windows on the north side of the house to let natural sun light warm up the slab.

   It seams to me that the slab represents a massive thermal mass that could be exploited to my advantage. Without raising the floor level or having access to run pipes underneath I am unsure if there is a method that I could use to utilize the thermal mass of the slab.

   Is anyone aware of a way to use my slabs thermal mass??

   Posted Sunday 6 Nov 2016 @ 12:20:45 am from IP #
2. 

   dave lawrence
   Member

   put some north facing eindows in, but make sure there are adequate eaves to provide summer shade. 900 mm or so depending n your latitude .

   Posted Sunday 6 Nov 2016 @ 7:04:25 pm from IP #
3. 

   Catopsilia
   Member

   Hi MrEGuy
   I think your title beginning with "using" points to a common problem in thinking about thermal mass.
   Thermal mass in a house stabilises the temperature. It stops the house getting either as hot or as cold as the surroundings.
   You have some thermal mass in the form of a slab and earth material under it. That is already stabilising the house temperature to some extent. You could verify that by using two cheap "Indoor/Outdoor" thermometers. Put one of them them in a room with the slab and one in a room without the slab, and stick each "Outdoor" sensor to the floor. In the course of a normal sunny day the sensor on the floor slab should vary much less than the other three sensors.
   I infer from your question that the slab would only be made "useful" if it were warmer than it is. Various techniques might work. One must ask how well? and at what cost?
   If there is no practical, cheap way to warm this slab, you might consider covering it with insulation to shut out its effect.

   Posted Sunday 6 Nov 2016 @ 11:13:17 pm from IP #
4. 

   MrEGuy
   Member

   Catopsilia,

   You are correct in stating that I was thinking about it in the wrong way. I wasn't thinking of it in a passive sense but actively charging it with heat or coolth like a battery.

   The house is quite pleasant compared with the ambient temperature. So it is probably already doing its passive thermal mass thing.

   Windows will be something to consider in the future. There are two bedrooms running along that wall and the rooms are best configured with their bed heads on that north wall. A 450mm high horizontal window might be an appropriate option. The eves are only 200mm on that side. A small retractable awning sounds like a good option (less involved than extending eves).

   It also sounds like tiles would be the best floor covering to conduct heat to the slab? I will take this into account when floor coverings are changed in the future.

   As for actively charging the slab, it sounds like running the A/C through the day when I have excess solar power might be the simplest cheapest and least invasive method. I assume that it will take time for the slab to absorb or release the heat, so I assume it would be best to running the AC on low power for a long period of time would be the best method.

   The only other active method that comes to mind would be to raise the floor level 100mm and install a hydronic system to charge the slab. I don't think I would be likely to go down that road but its good to know the options. Is there any other effective options out there?

   Would love to know your thoughts on above ramblings.

   Posted Monday 7 Nov 2016 @ 8:36:23 am from IP #

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