Post date: Oct 11, 2014 2:11:16 PM
The house I’m staying in is heated to a constant 69F. This is a bit cool for me to take a shower, even though I have done it for over a week. So yesterday I thought I would warm up the bathroom a bit before I shower.
At 4:30 am I woke up and remembered to turn up the thermostat to 72F. I thought that a couple of hours would be plenty. [In our Seattle house we have hot water radiators and when the water circulated by gravity it took about two hours to heat the house. (Now with a pump in the hot water line it only takes about 30 minutes.)]
And, indeed, by 7 am the room felt warmer. The thermostat indicated that the heat was still on (not yet up to 72F), but warmer. I took my shower and turned the heat back to 69F, figuring that was enough. Not so. By mid-afternoon the room was probably 72F (I did not look). The house continued to warm during the day, and now, at 7:30 pm it is well above 69F.
One of the touted advantages of a well-insulated house with a concrete floor slab is that the temperature doesn’t vary much. To me this might be a disadvantage, because you cannot have the bedroom cooler at night and warm quickly in the morning.
Thus the method of heating that I have chosen (subject to validation by a local heating engineer) uses a forced hot air furnace. This is heresy around here, where radiant floors are king. I know a furnace will heat the house quickly. It may not heat the floor slab quickly, but I only want the air warm.
And if it is only a warm shower that I want, then a radiant heater in the bathroom is the best solution. Radiant heaters are used in the outdoor seating areas of restaurants, and I know from experience that the sensation is very pleasant. The same sensation as sitting by a hot fire or wood stove. You may be cold on one side and hot on the other side, but comfortable.
Radiant heaters work quickly and do not have to heat the entire room or floor slab - they heat the body. And an electric radiant heater sells for about $100 - far less than many other types of heat. They do not require special venting (as would a stove). They can be mounted right up under the ceiling. I think I will try one. This I can do without a heating engineer!
The main heat for my house will be solar. Passive solar. That means no pump, no special panels. The method is called a Solar Slab, and has been mainly used only in northern New England. It is (to me) very logical. Under the concrete floor are air ducts. The room air is forced through these ducts (well, I guess it is not entirely passive) by the blower in a forced air furnace.
Only when there is a string of cloudy days and very cold temperatures do we need to use the gas burner in the furnace. The rest of the time the sun warms the air in the room (by shining on the floor, rugs, and furniture) and this heat is transferred to the floor slab.
The ducts under the floor are made of cement building block, laid on their sides so that the channels form air ducts. The air is pulled under the floor through registers (slots) near the outer walls and up through a sheet metal duct to the furnace fan. Very simple to build using standard components.
The trick is to size the thickness of the floor slab for the optimal thermal mass (to get through a winter night) and the size of the windows (to warm the slab during the day without overheating). So I hire a heating engineer.
I will learn to take my shower in the evening after the sun has warmed the house all day. Or rely on the radiant heater in the bathroom.