Building a new house in Palo Alto

Building a new house in Palo Alto

Saturday, January 5, 2013

Alternative Energy: Radiant Heat FTW (for the warmth!)

One of the features of our new house that I'm most looking forward to is radiant heat. I'm writing this post from our house in Mountain View which feels like an igloo. Our furnace is running full blast right now and I'm wrapped up on the couch in sweats, a turtleneck, wooly slippers plus an extra blanket and furry dog on my lap trying to stay warm.

We are working with the highly recommended team at Alternative Energy to install our radiant floor system. The hydronic (liquid) system will circulate heated water from a boiler through a series of plastic tubes embedded in the floor. We are also using this same boiler to supply our hot water throughout the house, except for two small tankless water heaters that will supply instant hot water to the upstairs bathrooms.
The tubes are rated for a 12" reach but tighter layouts result in more even heat. Ours were spaced at 6-9".

Here are some of the advantages of a radiant floor heating system:

Comfortable: No more cold feet! Radiant heat creates a more even heat throughout the house that is warmest at the floor and furniture level (where you need it) and cooler towards the ceiling (forced air does the exact opposite). Since our body temperature is warmest at our head and circulation is poorest at our feet, people are generally more comfortable in a room that is warm at the floor and cooler at head level. Another added benefit is that the air doesn't get dry like with forced air systems.

The tubes all connect to a water boiler located under the stairs. Pretty sure this will be the hot spot where the dogs camp out in the winter.

Clean: Unlike forced air heating which blows heat--along with dust, odor and germs--around the house, radiant heat doesn't use ducts and creates only gentle room air circulation. The flip side of this is that without any ducts to the outside, the air can get stuffy so you'll want to occasionally open your windows or run a whole house fan to allow fresh air in. Radiant heat is really good for allergy sufferers and pet owners since it doesn't spew allergens and dust bunnies around the house.

Customization: It's easier to zone your house with radiant heat, allowing various areas to be controlled by their own thermostat. We have the kitchen and family room on one zone that can be kept warmer than the bedrooms since we like sleeping at cooler temperatures. We also put the rooms we won't use as often (the office, living and guest room) on their own zones that can be kept off.  The bathrooms each have their own zone and can be programmed to warm up before we wake up...woohoo, no more freezing cold tile first thing in the morning. You can also run the tubing in tighter patterns in rooms that you will use a lot and wider apart in the areas you don't need to be as warm.
For fellow showeraholics...don't forget to run the tubes in the shower AND on the bench! 

Quiet & Durable: Radiant heat is quiet since there are no furnaces, blowers or pinging radiators. The plastic tubing is embedded in concrete so it is virtually indestructible as long as you avoid nailing into your floors. Our floors will include engineered hardwood, carpet and tile, all of which will be glued down on top of the concrete. Because our system is built into a thin layer of concrete (~1.5" thick) above the subfloor, it's much easier to repair than a system built into a thick slab foundation. It also avoids damage caused by settling. Note: You want to be sure to have your cabinets planned out ahead so that you can avoid laying down tubes beneath them.

After the tubes are pressure tested for leaks, they are set in "gypcrete"-- a thin layer of concrete. The orange square marks where one of the legs from our island will be nailed down.

Efficient:  Since there are no drafts with radiant heat, the average room temperatures can be decreased by 3 degrees to 6 degrees Fahrenheit. Cold feet make your whole body feel cold, whereas warm feet does the opposite. Because the high surface temperature of the floor warms your feet, I'm told that most homeowners with radiant heat are comfortable with a lower thermostat setting around 65 degrees. We generally keep our forced air system at about 67 degrees and I'm always freezing in our house (high ceilings don't help matters). The prospect of have toasty bare feet in the winter sounds like a dream to me.
Voila, welcome to our roller rink. We'll be gluing down engineered hardwood, carpet and tile (no nails!)

The main disadvantage of a radiant heat is that it's quite a bit more expensive than traditional forced air systems (although it has a lower operating cost).  I don't have the final amounts yet, but I suspect it'll be approximately 20K more than a forced air system. Also, because there are no ducts, if you want to put in an air conditioning system, you still have to pay to do the ductwork (which in our case would've cost another 10K). With our heavily shaded lot, we decided we probably won't need air conditioning.  However, we did hedge our bets and spent $400 to run a condenser line up to the roof in case global warming changes our mind down the road (this type of work is much cheaper now when the walls are open). Because we have open attic space, we can always add the ductwork later. There are also radiant cooling options that work off of the same system but again, we didn't think we'd use it enough to warrant an additional 10-20K investment.

In my opinion, if you're building a new custom home, radiant heat is one the best upgrades to indulge in. It requires a little extra time and advanced planning (your architect will need to put it in your building plans) but your toasty paws will be thanking you for years to come.
Even the haters are gonna love bath time with our new heated shower floors & bench.


  1. another nice feature , less worry about the heated air rushing out when a door opens
    as your not heating the air with radiant

  2. Hi,

    I have a quick question about your blog, do you think you could e-mail me?