EcoHome is in the process of building our next demonstration low-energy house, and to do so we have partnered with a company that manufactures frost-protected shallow foundations (slab-on-grade) that are heated with air rather than liquid. There are many advantages to air-heated radiant floors over hydronic radiant floors, but none greater than the ability to inject solar-heated air into the thermal battery which is the concrete slab floor. 

Passive Solar air-heated radiant floor slab on grade forming kit © Ecohome

Solar air heating panels are a growing trend in green building online, with one notable shortfall – the heat that is generated is difficult to store or control. Many people take advantage of the relatively simple and affordable nature of air-heated solar panels (compared to photovoltaic panels) to harness the energy of the sun to heat garages and workshops, but solar radiant air-heating has yet to be a viable and reliable option for well-balanced home heating. Until now ….

When looking for a heat-storage solution that would allow us to incorporate solar-air heating panels into our design in an "engineered" and reliable way, we approached Legalett, a manufacturer of slab-on-grade insulating concrete form kits for problem soils and air-heated radiant floors, to see if high efficiency solar air panels could feed air directly into their existing in-floor duct work. They welcomed the challenge and engineered the system that will be the main heat source of our new (as close as we can get it to ) Zero Energy home. Needless to say that we will be incorporating high efficiency insulation and air tight building envelope just like Passive House design. 

Legalett's existing radiant floor heating process consists of a closed-loop network of 4-inch tubes running through the concrete with a heater box embedded directly in the floor. In this case, added to that system are 6-inch tubes (seen in video) that will feed air to air solar panels on the south wall of the house. Air heated by those solar panels in winter, when the sun's angle is lower, will be fed into the floor heating radiant system, which will reduce the energy demand on the heater coil. Conversely and cleverly, in summer if the heat isn't needed in the house, the heat is diverted to an air/water heat exchanger for heating the hot water tank instead. What this adds up to is Energy savings; ideal for Passive Solar Homes, ZNE, PNE, LEED & Passive House projects

If you are interested in getting a quote for a Legalett air heated slab floor forming system, see here

Passive Solar radiant air-heated floor slab on grade form kit ductwork © Ecohome

Generating solar domestic hot water when heating is not required also serves to protect the panels from damage that can occur due to overheating in summer.

In the springtime, our pre-fabricated house with dense-packed cellulose walls will be delivered and installed on the slab. Below is a short video of the solar heated floor slab construction, stay tuned for more on the house that will be seated on it!  

For more reading and videos on pre-fabricated engineered insulated slab on grade form kits for problem soils like expansive clay see here, to read more about Passive House Certification see here, from the EcoHome Green Building Guides