Concrete Floor with Hydronics

The Delaney House I mentioned a few posts ago, a house that was lifted and moved on its own lot, in order to 1) make room for the Cheney Cottage to be move there from the UCB Campus and 2) make more space below the main floor level.  Actually, in this project the main floor level became the bedroom level and the more public spaces were moved downstairs.

With the Delaney House in its previous location, there was about 5-1/2 or 6 feet of headroom, so the house only went up about 3-1/2 feet.  The old foundation was completely removed and the new foundation was poured in two parts:  First the perimeter foundation and isolated piers for beam support were put in place.  Then, about a week ago, the Slab-on-Grade (SOG) was poured. 

Oftentimes, with S.O.G. floors there is a heating system, that pushes warm fluid around in tubes, embedded in the concrete.  We discussed this possibility at length, deciding to nix it because of the expense, then changing course and including it after all.  However, the tubes (called pex tubing) were not embedded in the concrete pour done last week.  They will be in a topping slab.  This is the way I prefer to do this kind of heating (called hydronic heat) because a barrier can be installed between the two slabs, and the lower slab, which is more massive, won't have to be heated up each time the thermostat kicks on.

One of the drawbacks to hydronics embedded in the main slab is that there is a long delay time between when the hydronics kick in and when the room actually starts to feel comfortable, because the slab is still warming up.  Even some of the gravel and soil beneath the slab get warmed up in those circumstances.  Not to get your hopes up too much, the topping slab also takes a while to warm up, but the lag time is reduced noticeably by the separation.

In this particular project, since this is a house with a history (built circa 1888), my clients preferred to have a hardwood floor.  So the hydronics will heat up the topping slab, which is on top of a barrier that also forces the heat upward, away from the slab below and up through the hardwood floor.  Typically, I prefer to let the topping slab be the walking surface, but the decision was that this would be too modern for this house.  So we'll be getting the best of both worlds - a traditional floor with modern heating.

The upstairs, which formerly was the only floor, will have radiators running on the same system.  This is still a Single Family Residence, just twice as large as before.  With hydronics, different areas, even ones that don't have doors separating them, can be zoned to heat separately.  This way, if the lifestyle of the occupants is such that the upstairs is only used at night, the radiators can be scheduled to warm up only in the evening.

In closing this post, one thing to mention about this form of heat is that the mechanics take up much less space - there is no need for ductwork or return-air plenums and the boiler can be small, about half the size of a forced-air unit.  There is a need for a room with valves spread along a wall, but that room can also be used for other storage or utilities.  And, the water heater can double as a heat-exchanger to power the hydronic system.  There are many ways to configure these systems, including the use of solar heat.  The extra expense is worthwhile in the long term and if you want to be green add this to your expansion plans.

3-D classes

The 3-D modeling continues apace.  However, I'd be totally lost if it weren't for the classes I've taken at the San Francisco Institute of Architecture (SFIA).  Dylan Steeze has helped me avoid many pitfalls, though much of what he showed us is still to be included in my practice.  Practice, practice, practice - haven't done enough of that.  So - back to the virtual drawing board.

Before signing off, I have to add that I still really have a lot of resistance to this way of working.  Drawing by hand is so much more rewarding!  Why is that?