Question

Is hydronic radiant flooring better than electric in terms of cost, heat generated, and installation ease?

Asked by Sapna
Washington, DC

I am turning a 700 sq ft basement into an income unit and want to install a ductless mini-split for heating/cooling. My HVAC consultant is pushing for a traditional system because he says the mini-split doesn't give off enough heat. If I install radiant flooring, will that compensate, and is it worth the cost? We haven't installed the concrete slab yet, so we have the opportunity now.

Answer

Randy Potter

Answered by Randy Potter

Santa Clara, CA

EarthBound Homes

July 9, 2011

Radiant floor heating can be a great way to heat living spaces. However, like most systems in a home, there can be upsides as well as downsides.

How radiant heating works

You must first understand that radiant heating works differently from traditional forced-air heating in that it heats up at a very slow rate and then maintains that level of warm feeling for much longer.

  • The feel of the warmth is different from a forced-air system.
  • Heat radiates from the floor and actually warms everything on the floor.
  • (This includes floor coverings like carpet or tile, as well as anything that sits on the floor, such as furniture.)

This type of heating tends to feel warmer to occupants in that everything you are exposed to is actually warm, rather than just the air; this is known as thermal radiation.

As far as cost of installation, any radiant system is going to be far more expensive than a mini-split (which we highly recommend) or a traditional forced-air system.

Costs

As far as electric vs. hydronic radiant heat, hydronic is always going to be more expensive to install than electric since there is more equipment (a unit to heat the fluid as well as a closed system of pipes under your floor) and it is more labor intensive and far harder to install.

Electric radiant systems basically consist of a mat that contains the heating elements which simply gets rolled out under the floor or concrete.

The real question is the cost of operation, and here there is simply no comparison; electric resistance heating is absolutely the least efficient way to heat a house.

  • The only compelling reason we have ever had to install an electric-resistance radiant heating system is when a client has wanted to heat a very small bathroom floor and it only needs to be heated for short periods of time.
  • This usually comes up when someone is showering in the morning and we can set the radiant heat system up on an automatic timer so it goes on for a short period of time first thing in the morning.

The other circumstance when we would consider it would be if a client was overproducing electricity with an oversized PV system and had extra power to "waste."

You do have some advantage, since you have not installed the concrete slab yet; however, you will still be paying a lot more money (at least double) for a radiant system than for a simple self-contained air source heat pump mini-split system.

Mini-split system

Mini-split systems are highly efficient and have both heating and cooling ability; that way you can keep your basement cool during the summer as well as warm during the winter.

The only technical issue you may face is that you need an exterior penetration to install the mini-split unit, so you have to have access to an exterior wall that is above ground or face a potentially more costly ducting scenario.

Making a decision

As we advise most of our clients, you should first figure out if radiant heat is really what you want from a comfort standpoint.

  • Make sure the very nature of the way it heats will work for your lifestyle.
  • (It heats up slowly and should be left on for long periods of time rather than operated "on demand" when you feel cold).

Once you determine this, you can find out the cost of installation and operation and then make a fully informed decision regarding which system will work best for your space.

 

For more information:

Read "Should I go with an air source heat pump or electric radiant floor heat?" a Q&A answered by Rick Goyette.

Tagged In: radiant heat, heating cooling

Do you have a question about greening your home? GreenHomeGuide invites you to Ask A Pro. Let our network of experienced green building professionals – architects, designers, contractors, electricians, energy experts, landscapers, tile & stone specialists, and more – help you find the right solution.