Underfloor heating and cooling suspended floors

You can enjoy superior underfloor heating and cooling if you are renovating or building with suspended floors.

Use a heat pump as the heat source to have reverse cycle cooling in summer as well. This will absorb heat from your home and expel it outside in reverse cycle mode.

For underfloor cooling, install a thermostat with a humidity sensor to ensure your floor stays above the dew point. A floor temperature of around 18 degrees in summer is about right. This will keep your floor above the dew point. 18 degrees is also pleasant to walk on with bare feet and sufficient for effective cooling.

Underfloor cooling works best in dryer southern or inland Australian climates. For the most effective underfloor hydronic cooling, install ceiling fans to circulate air across the floor. Also, you will feel about 4 degrees cooler as soon as you turn the ceiling fan on.

You can apply most types of floor coverings over your underfloor heating circuits although tiles radiate and absorb heat best. Other acceptable floor coverings include engineered timber boards, vinyl and open weave carpet. However, their thermal resistance should be less than 0.15 m²K/W for effective heating and 0.09 m²K/W for effective cooling. Thermal resistance of floor coverings higher than this will make your underfloor heating and cooling system less responsive and less effective.

Underfloor heating will be more expensive than radiators. Therefore, you may consider underfloor heating and cooling the suspended floors of your living/family room with radiators in your bedrooms. 

Three approaches for underfloor heating and cooling suspended floors

There are three reasonable approaches for underfloor heating and cooling your suspended floors:

  1. Minitec underfloor heating and cooling circuits, which will raise the floor level by just 15mm
  2. Expanded polystyrene lightweight panels, which have high compressive strength but will raise your floor level by around 30mm
  3. Aluminium diffuser plates fixed between the floor joists with insulation underneath to minimise heat loss, which will raise your floor level by less than 1mm.

1. Minitec underfloor heating and cooling

Minitec can be laid directly onto your suspended timber or concrete floors. This thin capillary hydronic system will raise your floor by just 15mm. The pipes have a diameter of just 9.9mm with 1.1 mm wall thickness and laid close together. Therefore, your underfloor heating and cooling system will be very responsive. You will begin to feel it in about 20 minutes.

Image shows thin profile of Minitec for underfloor heating and cooling on suspended floors
Minitec thin profile hydronic heating and cooling on suspended floors

 

Installation process:

  • Glue the base board onto your floor to give a secure bond for floor finishes.
  • Press the thin PEX-A pipes into the base board. 
  • Gather the flow and return pipe ends inside a cabinet or service room for connection to a manifold.
  • Pour a self-levelling fluid screed over the circuits.
  • Apply floor finishes onto the screed once it has set.

2. Expanded polystyrene panels Uponor Siccus FX is one quality brand of expanded polystyrene panels to consider. They are lightweight and have very high compressive strength. Being lightweight, they are ideal for timber suspended floors. They have an aluminium surface which is very conductive and responsive. The aluminium surface will disperse the heat evenly under the finished floor. You will begin to feel the underfloor heating and cooling in about 20 minutes. 

Pre-formed grooves in the panels are designed to fit 16mm PEX pipe snugly underneath the floor surface. Expanded polystyrene panels are 30mm thick.

Expanded polystyrene panel contruction over suspended floors

Installation process:

  • Lay the expanded polystyrene panels onto your floor.
  • Press the PEX pipe into the grooves of the panels.
  • Gather the flow and return pipe ends inside a cabinet or service room for connection to a manifold.
  • Lay thin cement sheets over the panels and PEX pipe.
  • Mark the pipe locatiion  underneath.
  • Nail down the cement sheets to the suspended floor.
  • Apply floor finishes onto the cement sheets.

3. Aluminium diffuser plates

Aluminium diffuser plates are fixed between floor joists with insulation batts underneath. This will minimise heat loss underneath the floor.

Aluminium diffuser plates are highly conductive. Therefore, they can disperse or absorb heat quickly and evenly underneath the floor. You will begin to feel the underfloor heating and cooling in about 20 minutes.

Structural flooring is laid over the diffuser plates on top of the floor joists to create the flooring substrate. Make sure your floor joists are set at 400 mm centres consistent with the common width of the panels. The diffuser plates are designed to take 16mm PEX pipes.

Aluminium heat diffuser panel construction between joists of suspended floors

 Installation process:

  • Push insulation batts between the joists with a snug fit.
  • Fit batons to the joists to hold the diffuser plates firmly underneath the flooring for good connection and conductivity.
  • Press the PEX pipes into the grooves of the diffuser plates.
  • Gather the flow and return pipe ends inside a cabinet or service room for connection to a manifold.
  • The flooring substrate is laid over the aluminium diffuser plates and nailed to the floor joists.

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