In-floor heating options

Rich L.

Barbra, you say it takes "longer to heat than normal" but what are you thinking would be normal? Part of the beauty of radiant in floor is the slow reaction times. This way when you get to the desired temps your system will generally stay pretty close to that setting with out temperature swings.

As mentioned above using a setback thermostat is not recommended with in floor. This is because of the long reaction times.

Recommendations, Not much oil used in my area so I'm not too familiar with that. You may see some savings if you tied in outdoor reset to your system. This would allow your water temps to adjust based on outside temps.

Good Luch, Rich L

Ralph Blaine_2

Cost efficient in-floor heating options

My house is built on a slab which, because of the site was required to be thicker than normal. The water tubes are deeper than they should be optimally. As a result, it takes longer to heat the slab than is usual. I am using a regular electric hot water tank with higher wattage elements wired together. It is working but it is very expensive. Does anyone have lower cost options for heating the water? Space constraints mean whatever I use must be compact. Propane is not an option as I cannot get the propane delivered here.

kpc_10

How about oil?

Or is that out of the equation too....was the slab insulated, both under and at the perimeter? If so w/ what insulation.
A godd ,properly piped oil boiiler would be an answer to the high electric bill.If that is out your only viable option left would bea wood boiler....Are you using a set back/programable t-stat w/ the radiant in slab? If so I suggest you find a temp and leave it at one temp...period. Setting it back at night will lead to long lag times and uncomfortable heat....kpc

Unknown

once it's heated up, it shouldn't matter. are you looking at initial startup cost or actual, "been running for awhile" operational costs?

Ralph Blaine_2

Time and Cost to Heat Up

Thank you for your advice.

I will try to answer all your queries here.

It took weeks to feel any warmth underfoot the very first time before I was living here, while the house was under construction ... an unfinished house, deepest winter, 1 ordinary element in the tank.

In September I had the elements wired together and upgraded and it took 4-5 days to heat the floor.

The breaker tripped (a faulty breaker) and by the time I realized (in January) the floor was quite cold again. Again it took several days to heat up and I used the woodstove as well.

I think with the two higher wattage elements and the extreme depth of the slab (10 - 12 inches) it is likely taking a normal time now to heat up, but my hydro bill for two months ... in Quebec where hydro is cheaper ... one person living quite frugally as far as power is concerned apart from that which actually runs the house (pumping water from lake, purifying it, heatline in winter etc.) ... was $640 (about $200 more than a neighbour who is also heating with radiant heat.)

It may be that I have been turning down the heat to 15 at night and keeping the thermostat at 17.5 during the day. I will try keeping it at one temperature as suggested. The thermostat is an ordinary wall thermostat situated in the front entrance way ... a pretty neutral spot as it is protected from wind and weather by a stone wall.

The thermostat in the water tank is set to 140 degrees Fahrenheit, I think.

Or it may be that the whole slab had to be heated up from cold twice because of the faulty breaker.

The slab is supposed to be well insulated (with something that looks like pink styrofoam I think) underneath and around it.

Oil is not a viable option here because of the road in and the steepness of the lot.

Would you advise me to keep the temperature at 17.5 all year round? Last summer it became quite cold and damp with the heat off, especially in parts of the main floor that were not as open to the rest of the house.

Or would that simply negate the good qualities of the in-floor system in summer? Maybe just open windows all summer?

Thanks for your help.

Barbara

Paul Pollets

Electric Boiler

I'd highly advise an electric boiler, rather than an electric water heater. Wiring the 2 elements to run simultaneously usually voids the warranty and can be dangerous. An electric boiler is designed for the load. Radiant slabs should not take more than 24-48 hrs to reach design temp on first startup. The slab depth is excessive for proper radiant performance.

See: www.electromn.com

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Unknown

holy cow.

did you say, 10 to 12 inch slab depth?

wow. that's a lot of concrete.

do NOT change your room temp. Perhaps turn off for summer, but skip setback entirely.

jp_2

slab thickness

are you sure about 10-12 inches thick? Or are you meaning 10-12 cm thick?

a slab 1 foot thick would take a long time for a simple electric water heater to heat. especially if cold as you say.

tomd7735_2

I would consider

abandoning the slab loop, and surface mount the tubing under a 2" built up floor. Faster response, reduce the heat sink/flywheel effect. With an outdoor reset control, and sequencer to delay power to the 2nd element so as not to trip the breaker. I wouldn't worry about setting the stat with a reset in the system.
Consider a geo or air to water heat pump?

ALH_4

Thick Slab

I hate to say it, but I agree with Tom. Depending on how low that tube is in the slab, you could have significant downward loss in order to bring the surface to the desired temperature.

Roth panels would probably be the easiest radiant floor retrofit and would provide some protection against that downward loss.

Personally, I would retrofit panel radiators and abandon the radiant floor.

Why was the slab required to be so thick?

Ralph Blaine_2

Re Suggestion to Abandon ...

I have considered abandoning the infloor heating and just using the airtight woodstove downstairs. I hate the thought of giving up on it though because I like the way it heats.

I cannot consider your option of installing a new heating system and floor. I spent a great deal of money installing a slate floor ... and am running out of money now anyway.

I will seriously consider using a boiler instead of the hot water tank, though. It will cost me $2000 to make that change, and if it saves me even $500 a year in heating, it will pay for itself.

By the way it is definitely 10-12 inches thick not centimetres. When they were pouring the concrete the loops were being buried very deep and seven men were trying to pull them closer to the surface. In retrospect it seems to me that the slab should have been poured in two stages with the heating pipes installed between. Hindsight is wonderful.

Thanks again for all the suggestions.

Barbara

Ralph Blaine_2

Why so thick?

Because the lot is very steep, the architect wanted to ensure that it would be stable. The road below the mountain is 39 steps up from the house, and the lake is 25 steps further down. The house is built on a plateau on a steep hill.

The site has caused all kinds of very expensive problems unfortunately. It is a beautiful spot but has been a builder's nightmare.

Barbara

Uni R_2

Savings

Unfortunately, the electric boiler won't be any more efficient for heating than the electric water heater. Both will get you the same number of BTUs for each buck you pay Hydro Qu

Rich L.

BTUs - Watts

I agree with Uni R, I don't see how an electric boiler could save $. Simply put: 3,415 btu's per KW electric. However I would anticipate a quicker reaction time from the electric boiler, depending on the number of elements called on. You could see a higher delta T across it which could help the slab react a little quicker. Of course you wouldn't want to send in too much heat and shock the slab.

Ralph Blaine_2

rocky ourcroppings

I have no idea. There are lots of those everywhere. I will call the architect. He would likely know. The original builder is not available for me to ask him, but there were a lot of photos taken as we went along.

What bearing would that have?

Barbara

jp_2

rock

if the floor was poured directly to the bedrock, good for stability BAD for keeping heat (in).

starting in cold weather really was a major hit on your energy requirements, needed to heat the whole and the near by ground as well.

highlander

heat calc

may need to do a heat load calc. on the house and size the input to that. once the slab is up to temp then its just maintaining the btu load.no on the setback.

tim smith

Does your lake freeze over in winter

What is your average water temp of lake water in winter. Just wondering if a lake loop heat pump could be used?? Allowed? May be a possibility.

Tom Manton

12\"

It doesn't matter that the tubing is to deep, or if the slab was poured in two lifts, conductance of the concrete will mean the entire slab will reach design temp anyway.

Dampness when the heat is off tells me insulation and vapor retardation are inadequate. JMHO, architect sold you a bill of goods on the 12" slab, there are many other ways to skin that cat.

energy detailing was either not drawn correctly, or not installed or monitored properly.

If as suggested you go over the slab it must (the slab) be isolated from the building envelope. 6mil poly 1.5" isocyanurate foam minimum. Leading us to a 2.5 to 3.5" buildup and the resulting detailing.

Sorry for the bad news, but proof once again, far easier to get it right from jump than repair it after.

As to energy input, I can't imagian that water heater providing it anywhere in Canada, especially if the envelope energy detailing is as bad as the slab detailing.

kpc_10

I think... paul's

suggestion was to go w/ the electric boiler based upon the electric water heater is being used in away that it was not designed to be used....
Barbara...do you have any pictues? how big is your place? how many tubing loops and how long are they? if they did not put enough tubing in the floor or made tubing runs too long that would have a bearing on the responce time also...kpc

Ralph Blaine_2

My Lake

Tim:

My lake is very tiny and it does freeze over. There are no motors other than electric allowed on the lake so I am not sure whether your suggestion would work. I have never heard of one of these ... but then I am the world champion of amateurs on all this.

I bring my water from the lake using a heatline to keep it from freezing.

Ralph Blaine_2

Size and # of lines

The slab is 900 square feet ... a two storey house ...

There are 3 loops on the original drawing but there are 8 places where the waterlines enter the floor in the utility room, so there are likely 4 loops. I know that the plumber changed the loops from the original plan.

What pictures would help clarify this?

Ralph Blaine_2

Bluestone

What would you suggest I use to heat the slab in view of your conviction that a) the slab and insulation are likely faulty and b) that a hot water heater is a poor choice in view of the Canadian winter?

Barbara

troy_8

Electric options

I work for Aht usa Inc. We sell a low mass very thin ribbon electric heating mat that is installed directly under the flooring. You would need to take up your finished floor to install this product. The advantage is, as long as you install a thermal barrier over your massive slab this system will give you very fast reaction time. Every room has it's own thermostat so it is very controllable. I think you need to abandon this ill designed system and not throw any more money down the drain that doesn't address the shortcomings of its design. To install a boiler is better than water heaters but it doesn't really address the problem. Check out www.aht-heating.com Call me any time 716-989-9878

Andrew Hagen_2

Tube Depth

It does matter how deep the tube is in the slab because the conductance of the concrete depends on the thickness. If there is more concrete on top of the tube than there is below, the bottom of the concrete will be warmer than the top.

I think your problem is that thick slab and the depth of the tubing. The architect should have planned to have the tube located a few inches down from the top, rather than near the bottom. An in-between option would be to use the tubing in the slab to maintain the floor at a tolerable temperature, but not try to heat the room with it.

I would then install steel panel radiators to provide the primary heat for the rooms.

I would also install a Laing EPR heater to replace the electric water heater. It won't save much energy, but it will improve the response time of the system.

kpc_10

a picture of...

the utility area would help us see the whole layout ans if there were piping issues that might slow the response time...ty,kpc

highlander

I understand this is a 2story house. how is the up stairs heated? what is the heat load? it seems a elec hot water heater isnt going to match the load

jp_2

yep

andrew is right. and whats makes matters worst is if the bottom of the slab has insufficient insulation, end up putting too much heat into the ground below instead of the room above.

Tom Manton

Andrew

You are right about the tube placement in a truly technical sense. In a properly thermal isolated slab the variance within the slab would be so small as to be considered nearly inconsequential. The difference with raising the tubing would be seen in response time. The backside of that equation is that once the themostat is satisfied,the heating flywheel effect would show a faster slowing as the slab tries to reach equalibrium. Read that to mean more peaks and valleys.

Sorry, I don't have a diffinitive answer to remediation, other than to say, any above slab method needs to be properly thermally isolated from the slab or the slab will continue to act as a heat sink ( also vapor retarded ).

I apologize for sounding terse, but I can't believe the ways we build homes in the 21st century and it certainly raises my ire when I come across these stories. ( been watching to much Holmes on homes I guess)

P.S. I'm no greenee treehugger but 30 years a energy wise builder, 1st energystar rated home in my area, and I live in a 4000sq/ft home in VT with r48 roof, r36 wall, large interior volume (12' and 18' ceilings) 6" slab infloor 1st level, 1.5" thin slab second level, a 68,000 btu heatloss (calculated), and use no fossil fuels for heating.

Ralph Blaine_2

Heat Load? Upstairs Heating

The upstairs has two bedrooms with baseboard heaters which almost never have to run because the warm air comes up the stairwell. There is a baseboard heater in the laundry room and a forced air electric heater in the bathroom, neither of which ever seem to go on now that the downstairs is warm.

If I have a fire in the woodstove it actually gets too warm everywhere, including upstairs.

I don't understand the term heat load.

Ralph Blaine_2

The Overwhelmed Amateur

Thank you to all of you. I really appreciate the time you have taken to help me solve this problem.

I am feeling a little overwhelmed by the information load just now. I think I will try to process the different views and come to some kind of conclusion about what to try next.

I am leaving the thermostat at 15 degrees night and day just now and am feeling comfortably warm.

I will also take a look at the next hydro bill and see whether the fact that slab does not have to be heated from cold during this heating period, and keeping the thermostat at 15, makes a difference.

Thanks again to all of you.

Barbara

bob eck

what about installing solar panels and using a solar water heater with one coil for the solar panels and the tank would have a electric back up element in it?

are you in a area that is not shaded? you would need to put the panels facing south.

just a suggestion.

good luck

bob eck

what about installing solar panels and using a solar water heater with one coil for the solar panels and the tank would have a electric back up element in it?

are you in a area that is not shaded? you would need to put the panels facing south.

just a suggestion.

good luck