Radiant Floor Heating
Radiant floor heating is one of the most common requests we receive from custom home design clients but does it make sense for your new home?
We discuss radiant floor options, installation methods and advantages/disadvantages.
On almost every project, our clients ask for some form of radiant floor heating in their new Custom Designed Home. The conversation usually leans towards whether the a radiant floor installation carries enough benefits to offset the initial cost. While having a higher up-front cost than conventional forced air mechanical systems, radiant floor heating can be a great solution if used and installed properly. To determine if radiant floor heating makes sense for your new home, it helps to understand exactly what it is, the most effective way to install it and whether it makes sense for your new house.
What is Hydronic Radiant Floor Heating?
The most common installation of radiant floor heating is the hydronic system. A hydronic radiant floor is composed of plastic (PEX) tubes that carry a mixture of water (and/or glycol) heated by a boiler to different zones throughout a house. The heated tubes then radiate heat throughout the room providing for a very even and consistent temperature.
Any type of flooring (eg. tile, laminate, finished concrete, hardwood, carpet etc.) can be used on top of the radiant floor making it very versatile. Something to keep in mind is that the type of flooring can have an impact on the effectiveness of the installation. For example, tile or finished concrete slabs are generally better than hardwood or carpet because wood flooring and thick carpet acts as an insulation blanket, can restrict upward heat flow and reduce the efficiency.
Recommended Installation Methods
The PEX (cross linked polyethylene) tubes carrying the water/glycol mixture are either encased in a concrete slab, a gypsum cement over pour, Warmboard subflooring, or suspended below a wooden subfloor with metal fasteners.
Hydronic Radiant Floor Heating Installation in Concrete Slabs
The most effective hydronic radiant floor system we recommend is to install the PEX tubing directly into a concrete slab. Concrete has a high thermal mass and so it is much better at retaining heat than wood which means the system can be turned off and still emit heat for an extended period of time. In a typical 4" thick concrete slab on grade installation, the PEX tubing is installed in the middle of the concrete slab. In thicker concrete slabs the tubing should be installed 2" to 3" maximum from the top of the finished surface. It is extremely important that the concrete slab is insulated below the slab as well as on the slab edge or foundation wall otherwise the heat generated will be lost to the cold ground beneath the home. R12 rigid insulation is the minimum required by the British Columbia Columbia Building Code but if possible, we always recommend more insulation. Insulation is one of cheapest building materials and so it pays in invest in keeping the heat (energy) inside the building enevelope as it will reduce your overall monthly energy bills.
Warmboard Hydronic Radiant Floor Heating Installation
Another very effective solution is to use a Warmboard type product that effectively and efficiently conducts heat through its aluminum top sheet. Warmboard panels are a significantly better alternative to having the PEX tubing installed in joist cavities. Warmboard is great for both new construction as well as renovations and additions because a concrete slab is not required. Warmboard comes in two particular forms, one product is composed of a structural plywood subfloor and the other product is a non-structural OSB which can be installed over an existing subfloor making it more suitable for renovations.
Warmboard subflooring includes an aluminum topsheet which is coupled with tubing that is also lined with aluminum which provides very efficient heat transfer.
Where Warmboard makes the most sense is in a home where the Owner would prefer to have radiant floor heating throughout the entire house. Typically, most homes basements are concrete slabs but the main and second floors are wood framed using wood joists or engineered silent floor joists. Considering we do not recommend installing PEX tubing in the floor joist cavities, this is where Warmboard is an excellent solution. The Warmboard plywood subflooring is installed over the floor joist framing just like regular subflooring and it comes with pre-routed channels that the hydronic tubes are laid into. This allows for easy installation and the entire home to by heated hydronically.
Warmboard is unique in that it includes highly conductive .025" thick 1060 aluminum that covers the entire panel surface as well as tubing that that is lined with aluminum.
DO NOT DO THIS! Hydronic Radiant Floor Installation in a Joist Cavity
We do not recommend installing PEX tubing beneath a wood subfloor inside a floor joist cavity.In these installations PEX tubing is secured to either the joist or subfloor with metal fasteners and then batt insulation is installed beneath the tubing inside the joist cavity. The heat produced from the tubing is not effectively transferred to the floor above because there is no thermal mass within the joist cavity, no effective conductive material for heat transfer and the plywood subfloor as a barrier which restricts the upward flow of radiant heat to the floor above.
Radiant Floor Heating Advantages
Energy Efficiency – When the ideal temperature is reached within a specific zone, the radiant floor can actually be turned off completely and because water and concrete are great heat retainers, the temperature will remain constant for an extended period of time. This will save money through heating costs because the system won’t have to be on as long as other heaters.
Room Function – The radiant floor tubing is hidden within the floor assembly allowing every square inch of the space to become useable. For example, no dropped bulkheads to hide forced air ducts or electric baseboard heaters on walls.
Comfort and Cleanliness – The system contains a properly sized circulator pump which slowly moves the water through the PEX tubes silently. The only noise comes from the heat source, located either outside or in a separate utility room making the system almost invisible. Additionally, unlike traditional baseboard or forced air heaters, there are no “hot spots” or varying room temperatures throughout the zone, adding to comfort. Another added benefit to radiant floor heating is cleanliness. Without having to use air ducts to move air around, dust particles in the air tend to stay put, which can be beneficial to people with allergies.
Controlled Zones – Each zone throughout the house, while being hooked up to only one heat source, can be controlled separately. Most radiant floors are installed in rooms that are either used the most, or rooms that will have the coldest floors. Tiled surfaces such as bathrooms and kitchens, and frequently used spaces such as living rooms are the most common. Where there is a higher solar gain on one side of the house it makes sense to have a separate zone.
Multiple Energy Sources - one of the great benefits of radiant floor heating is energy source compatibility. This allows the homeowner to choose from a number of different sources to heat the water. These can include boilers heated with electricity, gas, oil, or wood, a ground-source heat pump, and even solar hot water panels. More often than not, boilers tend to be the norm because of their low cost and easy installation, however solar power is becoming a popular choice as well.
Solar Hot Water panels collect energy from the sun which is then transferred to the boiler system using a heat exchanger. The sun is the largest free source of energy on earth!
Radiant Floor Heating Cost and Maintenance
The biggest disadvantage to using radiant floor heating would have to be the cost. Typical costs for a hydronic system within a concrete slab are $6 to $10 dollars a square foot, and that’s just for the tubing. There is also the cost of the heating components and controls, which can run you anywhere from $3,000 to $10,000 for a two-thousand square foot home depending on the configuration used. When compared to other heating solutions, the initial cost is typically greater for a hydronic radiant floor.
Maintenance can also affect the decision of whether or not to include the system in a home. Particularly, in a concrete slab installation, it is important to have the tubing functioning perfectly before pouring the concrete slab or laying flooring. If a tube were to rupture at any point in time, the first task would be locating the problem. Next you would have to remove a section of flooring, possibly break through concrete while avoiding other tubes, and then repair the leak. Fortunately, the cross-linked polyethylene tube or “PEX” tube, is incredibly durable making leaks almost non-existent. This is advantage of the Warmboard system because although you may have to replace some flooring and a Warmboard panel, no cutting of concrete would be required.
What do we recommend?
We work on all kinds of custom designed homes and depending on the type of construction and type of home, we believe that radiant floor heating can be a great option for your new home. Yes, it comes with a greater initial cost but the benefits of having a heating system where you can still heat a room while being turned off is quite appealing. And despite sounding like a lot of work to install and maintain, there are people who specifically design these floors to suit every home individually and with a skilled contractor the installation will be done professionally. Not to mention, you will be left with nice warm feet!