Extending Thermal Gain in a Home

Permaculture Home - extending a slab for thermal mass

Can we make our exterior walls and windows warmer – letting our floor capture more heat and radiate warmth beneath our feet during the cold winter months, by stretching out the structure to increase thermal gain from the sun?

I have a sketch that shows how the sun path can be designed into a home, how the roof eave and the window should work to use the summer sun and the winter sun. This is a well known concept in design (however I don’t know that we use it enough in practice. I for one have not seen it used on the projects I worked on at my place of employment).

To this sketch, I am adding an extended concrete slab that stops shy of where the summer sun would touch it. At this spot where sunlight hits, we change the material to wood which would feel warm and can breath in the summer sun.

…adding an extended concrete slab that stops shy of where the summer sun would touch it.

It may seem odd to have two different materials on your deck. You’d look down and see a warm wood deck, stained and sanded, with a muffled tap when you walk on it. It then transitions onto a concrete deck, maybe it still has a timber texture on it. I am sure there are ways to make this blend more with the rest of the home. Meanwhile, the benefit is a warmer perimeter in your home where it typically gets chilly in the winter.

Permaculture Home – extending a slab for thermal mass

I need to mull on this some more from a holistic perspective. Does it chill the interiors in reverse? Does this add to moisture? Constructability may be cumbersome.

This idea is in its infancy. The idea is that this allows you to extend your thermal mass to the outside, a bit further to the edge of the sun path, to bridge/store more heat in the winter. This should make for a nice toasty lounge with a view to the outside winter landscape, your feet enjoying radiant warm floors as you sip coffee. In summer, this thermal mass is shaded and should not add any discomfort to the same coffee drinking corner.

The idea is that this allows you to extend your thermal mass to the outside, a bit further to the edge of the sun path, to store heat in the winter

This type of detail is not difficult to implement, but is an extra step a designer has to take: to calculate his actual sun angles on a site. It is not easy to implement for mass housing. You’d have to adjust it for specific site orientation and conditions. This detail needs you to take a really close look at each side of the house, solar angle, wall and roof conditions and then determine the depth of that concrete lip.

This detailed solution is unlikely to scale for mass produced housing-but that is the point. These ideas are a luxury compared to mass produced housing.

For the scale of homes-not mass production-I am wanting, this can be implemented and is a long term solution. The initial cost is from the quality of design, there may be minimal increase in materials, but the return on investment is throughout the entirety of the house. Talk about a great energy audit from a permaculture standpoint. Heck if it works I am going to use this on all projects as long as it is appropriate.


My goal at Alt-Ark is to Make Architecture More Permaculture, to help you build that permaculture house on the homestead.