Radiant heat – luxury or necessity.
Working through all the bids and negotiating with subs has certainly taken some time. On top of this, our checksheets from the City of Portland for Structural and Soils were fairly lengthy. The architectural set of drawings referred to the structural set in many cases. The structural set then referenced the Geotechnical Engineer’s report. The City didn’t like this at all. They wanted all the Geotechnical information shown in the drawing set. Their argument is they don’t think a sub contractor would look in a report. Maybe slightly picky, but makes sense. We ended up making a new set of ‘Geotechnical’ drawings to add into our overall set….should work. We’ll submit them next week and see what happens.
In the mean time, we’ve been looking into the multitude of heating and cooling options. To get into some basic costs, the Warmboard floor sheathing we have specified in the house runs $22,000 (typical plywood sheathing is $3,000). This price includes a ‘trade’ discount, which is nice. On top of this, we have a radiant system that will run $15,000 – $20,000 for pumps, tubes and manifolds, plus water heating equipment (boiler, tankless or tank heater) at another $2,000 – $6,000 depending on the equipment. On top of this, we have very minimal insulation bids at $25,000 for full perimeter 1 1/2″ flash and batt to $35,000 for 3″ flash and batt. Flash and batt refers to a ‘flash’ pass of spray foam, followed by a less expensive batt or blown in insulation for the remainder of the wall cavity. My theory has always been to spend your money on a tight, well insulated building envelope and spend less on smaller, more efficient HVAC equipment that will use less energy during the life of the building. Keep in mind, we are building 8″ thick walls and 12″ deep roof diaphragm that needs to be completely filled with insulation. I did stray from my theory towards a more expensive and luxurious heating system that may cost up to $48,000 to install. In addition, because you don’t turn a radiant system off, you’re wasting energy while you’re away from the house during the day. A humbling exercise. We have determined our radiant system to be a fantastically wonderful luxury.
At the moment, we are getting bids on three systems:
1. hydronic radiant heat with a gas fired AO Smith Vertex water heater and another for domestic water
2. Fujitsu mini split ductless heat pump for heat / cooling, Vertex water heater for domestic water
3. Fujitsu split ducted heat pump for heat / cooling, Vortex water heater for domestic water.
Why not a tankless water heater? With the addition of the ADU in the building, we have a potential of 3 showers and 2 dishwashers running at the same time. This load if fairly difficult for even the best tankless to keep up with. Using a dishwasher with an internal water heater can help, but three showers at once is still tough to manage. We’re working with EcoHeat on pricing. We’ve found them to be extremely professional, knowledgeable and competitively priced.
Tags: HVAC
September 11th, 2009 at 12:15 pm
Agree on the tankless water heaters. We switched to tanks. Tanks have been around forever, they are cheap to replace, and there’s just a lot less to break. If in ten years, tankless technology has come even further along, you can always swap some in and get rid of the tanks.
With regard to radiant, I would have loved to do it, but as soon as you want air conditioning, you’re talking about installing two systems. If you stick with forced air, it’s all just one system. Much, much cheaper. We’re still going to do radiant pads in the master bath and in the concrete hallway, but that’s about it. Another consideration with radiant seems to be that it can’t react as quickly to quick changes in sun exposure. I have a ton of west facing glass, so on a cold day that all of a sudden becomes very sunny, the heating demands should drop pretty quickly, and vice versa when the reverse happens. Seems like forced air is just much better at making quick adjustments. Sounds like you are doing both though, right?
September 11th, 2009 at 2:59 pm
Mike –
We were going to do radiant with Warmboard. It can adjust much faster than typical ‘mass’ systems, but certainly not as fast as air. We were then going to ‘rough-in’ for a future heat pump just incase we need AC in the future. Thanks to the site, the South side of the house is basically built into the hill. 99% of the glass is North Facing and we have an R-50 rough with an eco roof on top, so our plan was to see how things went without mechanical cooling. Heat pumps are not easy to install cleanly due to the refrigeration lines, so roughing in during construction made sense.
Given the price of the radiant, we may just install the heat pump in lieu of the radiant system. We’ll then have heat and AC – just won’t have the comfort factor of the radiant.
The radiant pads are great! We’ve used them before and they work well. Setting them on a timer is a good way to go.
October 23rd, 2009 at 6:14 pm
I’m a little late to this discussion, and at the risk of sounding spammy, have you considered electric radiant systems instead of hydronic? They are considerably less expensive, don’t take up floor space for mechanical systems and don’t have any maintenance. I understand that your electrical rates are quite good compared to the national average, so your operating costs should be very good.
October 26th, 2009 at 8:18 am
We did look into one electric system from Step Floor, but the pricing was between $9 and $16 per s.f. – too rich for our blood. We are still considering something similar for focused locations, like the kitchen floor. In our last house, we had a combination of electric radiant floor heat with forced air and weren’t happy with it. I was always way too warm when my wife was comfortable in the areas with the radiant, and in the areas of the house without radiant, we were always cold because I was always turning down the forced air thermostat. The only place in the house we both liked it was the master bathroom floor.
October 29th, 2009 at 3:16 pm
Yeah.. at that price I don’t blame you.
Also, a mixed forced air and radiant system (unless the radiant system is sized just for floor warming) generally aren’t going to get along. The forced air system (usually with a single, centrally located thermostat) can’t measure the mean radiant temperature of the objects in the home. (It only measures air temperature in its immediate vicinity.) It can’t respond to radiant gains – whether that gain is from a radiant heating system or from solar gain, so it’ll merrily force more hot air into an environment which is perfectly comfortable without it.
And no heating system can overcome the man vs woman argument about what constitutes “warm enough”.