Electric Radiant or Hydronic Radiant floor heating?

contemplatingmonkey

Hi everyone
I am building a small garage house (laneway house) on the backyard of my property in Vancouver, B.C, Canada.
The proposed house is a two floor building. The basement has a 470 sq ft of area. And the second floor has a 150 sq ft of area. The total volume of the heating space is around 5000 cubic ft.
The house will be very well insulated ( under-slab R12, wall R22, attic and ceiling R50, window&door R5 up, Air Tightest ACH below 3.5 change/ hour).

The Design Temp Difference (DTD)= 53F -----> Vancouver outdoor design = 19F , Indoor design = 72F
The Heating Day Degree in Vancouver is around 3000 per year.
I have calculated the heat loss of the house would be around 9300 BTU/hr.

SO my questions are

1. since the house is small and well insulated, should i just install the electric radiant floor heating instead and forget about the Hydronic radiant floor heating? ( i like the idea of hydronic radiant floor heating, but i have a really really small mechanical room. i am afraid i would run out of installation space. )

2. has anyone installed an electric radiant floor as a heating source in a climate similar to Vancouver? how much is your avg electricity bill? how well is your place insulated? what is the spacing of your heating wire? what is the watt power of your system?overall, is it warm?


If i use the electric radiant floor heating system .......(please correct if i am wrong) Using the formula 1 BTU/hr = 0.29 Watts, and assuming i will operate 8 hours a day for 270 days in year and at 11.95 cent/kwh ..i will be paying around avg $58 per month in a year.

But theory is just theory. i hope you guys can share some of your valuable radiant heating experience here.
Thank you

Rich_49

What is your NG rate in the area ?

SWEI

We find that for small, well-insulated buildings in relatively moderate climates, electric resistance frequently turns out to be the best option. If you think you might want A/C later, I would seriously consider a ductless mini-split.

I'm somewhat curious how you get R12 under a slab. EPS and XPS in suitable compressive strengths are both ~R5 per inch. The cost difference between 2" foam board (R10) and 4" foam board (R20) is negligible, especially for a slab that small. Slab edge insulation is also important.

Electric resistance mats or cables will definitely cost less to install than PEX and pumps would, but it would represent a firm commitment to hydro. Far less of a risky bet in BC that that would be for most of us

RobG

You could also go with a Thermolec electric B-3TMB boiler and that way you will always have the option of switching fuel types down the road. They are small and wall mounted and have outdoor air reset. That model is 10,236 btu's, just about a perfect fit.

SWEI

Yes, I left it unsaid: It does cost a bit more, but a low temperature water-based distribution system gives you the ultimate flexibility with regard to energy sources. Solar, biomass, GSHP, you name it.

contemplatingmonkey

Hi Rich
I am not planning to install NG service.
But here is the NG rate.
The basic charge per day =$0.389
Delivery charge per GJ= $3.547
Storage and transport charge per GJ =$1.334
Cost of gas per GJ=$2.486


Hi SWEI
I have installed a mini ductless heat pump in my warehouse shop before. I think it is a very efficient system. But the compressor on the outside of the building is pretty noisy. I do not want to disturb my neighbor.

I am sorry about the under slab R valve. this will be more clear
"Foundation wall and under slab: on plan wall insulation meets or exceeds R22 effective, under slab meets or exceeds R12 nominal."


Hi RobG
I was also thinking about getting a electric tankless water heater for the hydronic radiant system. They look very compact, space saving, and efficient.
What is an outdoor air reset?
i can see the Thermolec electric B-3TMB boiler produce 10236 BTU/hr and consume 3kw and cost around $800 dollar.

Have you heard about the Eco smart electric tankless water heater? http://www.ecosmartus.com/products/radiant-floor-heater/
This electric heater seems to be designed for radiant heating as well, but alot cheaper.
Do you know the differences between these two brand of electric water heater?

Thank you for your replies guys i am glad i found this forum

contemplatingmonkey

Now, this question came to my mind.
will the electric hydronic radiant system use less electricity compared to the electric resistance mat? when both system are installed in the slab.

hot_rod

Every time you put energy thru a phase change, you lose some efficiency. Electric to a resistance should pencil out better than electric to water. Which would also require pump energy to circulate.

In the right application the electric cable or mat is a great option.

SWEI

contemplatingmonkey said:

What is an outdoor air reset?

It's a control strategy which raises the water temperature setpoint as the outside temperature drops. It's pretty much the only way to effectively manage a high mass emitter system.

i can see the Thermolec electric B-3TMB boiler produce 10236 BTU/hr and consume 3kw and cost around $800 dollar.

Have you heard about the Eco smart electric tankless water heater? http://www.ecosmartus.com/products/radiant-floor-heater/
This electric heater seems to be designed for radiant heating as well, but alot cheaper.
Do you know the differences between these two brand of electric water heater?

A tankless water heater (gas or electric) is designed to heat cold water to a preset temperature. I know of two ways you can add outdoor reset control to a system based on one -- and either will add ~$400 to the cost of the system.

Thermolec happens to sell the smallest electric boilers you can get in North America which include outdoor reset control. Electro Industries offers them starting at 10 kW.

Harvey Ramer

I would think carefully before putting electric heating cable in a concrete slab. It has no give and can easily be damaged from concrete movement. Tubing in slabs has a good track record, on the other hand.

Zman

Harvey Ramer said:

I would think carefully before putting electric heating cable in a concrete slab. It has no give and can easily be damaged from concrete movement. Tubing in slabs has a good track record, on the other hand.

Harvey makes an excellent point. Electric mats are much more vulnerable to physical damage than pex. They also tend to just plain wear out at some point.
It is going to be more difficult controlling indoor temp with the mats as they are a simple on/off device. With a water based system you can vary the water temp based on the actual outdoor temp (outdoor reset) creating a more comfortable indoor environment.

For comparing energy costs, this is an excellent tool
www.eia.gov/tools/faqs/heatcalc.xls

In most areas, either an electric heat pump or natural gas are the cheapest.

Carl

hot_rod

Yes the tubed system allows for a variety of energy sources, that may be a plus.

With a small space like that, a mat system would not require any mech space, and it very "zonable" right down to a small bath floor area. Electric systems can be setback, timed, and the outputs varied with PWM controls just like water based systems

My experience with the mat systems is they are very flexible and durable. If a 470 square foot slab has enough movement to damage it, or pex, you have bigger problems.

I'm a hydronic guy first and foremost, but I have learned for small areas, with electricity as the energy source, the mats are a nice optioned often ignored by wetheads

And a handful of PV modules could directly offset some energy cost. See if any programs are available to offset solar installations in your area

4Johnpipe

I honestly thought that electric radiant was only a secondary heat source or floor warming. Never considered it as a primary heat source. What manufacturers list their product as primary heating?

hot_rod

Generally they list the cable or mat by output in watts or btu/ square foot. Same load calc as a hydronic design, they just calculate the BTUs to watts.

I've worked with the Watts Radiant product, sold under the HeatWeave or Sun Touch brands. Also DeltaTherm, both are UL listed as heating products. DeltaTherm is listed for heating, snowmelt and roof melt cable.

There is a bunch of electric cable snowment in Utah including the sidewalks around some of the city buildings in downtown Salt Lake. Those downtown cable systems were installed 20 some years ago. Be interesting to see how many still function.

The class 2 snowmelt systems, for public access area, were designed around 100 BTU/ sq ft back in those days. That's probably why they had to bring on a second coal fired power plant

contemplatingmonkey

wow Hi Bob Rohr
i was just watching your videos on youtube not long ago.
Those videos are very education and helpful. And the Caleffi's product looks great. I was thinking i would get a caleffi manifold if i were to install the hydronic radiant.

i have spent some time on researching hydronic radiant.....i guess i don't get to apply it now..haha

Thanks everyone and thank you Bob

hot_rod

Stop monkeying around and start building! Good for you for taking the time to research all the options. Thanks for the nice comments.

tim smith

Electric cable is more what I have recommend than the mat when it is just a small load, ie bathrooms or small areas. Even if we are doing boiler with existing radiators as the extra cost involved in adding 2nd temp and controls just does not make sense.
Another interesting option for this small of a load if you need hot water too is a heat pump water heater, small braze plate heat x pump and tubing. A heat pump water heater then could supply potable and space heat. Not a big fan of water heaters as heating device but could be a very economical efficient means in this small of an application.

Paul Pollets

I use Orbit Alcatel cable for loads larger than 200SF, as mats get pricey beyond 200SF. The Orbit product is distributed from Perkasie, PA. It need to be embedded in a min of 3/4" mudset. Running costs are minimal at $.12/KW/hr.

contemplatingmonkey

Hi tim smith
Thank you for your reply.
what are the differences between mat and cable?

Hi Paul
Do you know about the EMF problem from the electrical cable system?

contemplatingmonkey

I have a found an unbiased report about the emf problem by the Switzerland government.
http://www.bag.admin.ch/themen/strahlung/00053/00673/05139/index.html?lang=en

It turns out that the LOW VOLTAGE TWO_CORE heating cable is the safest option.

The EMF strength is proportional to the voltage. Higher the voltage, higher the EMF.

jumper

You didn't ask but I would go with electric ceiling radiant. More comfortable (don't believe what floor radiant marketers). No worries about R value of slab. Faster response & better control. Less expensive. Contact BC Hydro for their opinion.

dscottmilner

Jumping in to converse about electric heating in the ceiling. Any success ?

dscottmilner

jumping on this conversation to ask about people's experiences with radiant ceiling heating

SWEI

Might be the same poster here. If so, he appears to be in AU.

Zman

SWEI said:

Might be the same poster here. If so, he appears to be in AU.

I agree.
In any case this site works better if you start a new post rather than piggy backing older posts.
Details about the particular project is also helpful.

Big-D

This little electric boiler will provide everything you need in btu with compact pre engineering designed with outdoor reset and gpm and psi indicators plus more. Check out www.nextgenboiler.com. There's a rep in BC