Underfloor Heating Systems

Underfloor Heating for Homes

There is no doubt that underfloor heating with water pipes in the slab is simply the best way of heating homes, and heating this water with a hot water heat pump is the most cost effective underfloor heating system.

As the pipes can only be installed before a slab is poured this option is only available for new houses. However converting an existing house from a diesel or gas boiler is often straightforward and will be much cheaper to run.

• High in comfort.
• Low in cost.
• Reduction in condensation.
• No fans required, reducing draughts.
• Cheaper than heating with diesel or gas.

Personally I would sacrifice a designer kitchen in order to put the pipes in as they cannot be fitted later. If you run short of money finishing the house off, leave the heating until later, it won’t go anywhere.

Case Study: Rangiora

Case Study: Cashmere

How does it work?

Floor heating with water pipes in the slab, (often referred to as hydronic heating): these provide space heating by low radiant heat transfer from the floor to everything in the room. The benefits are a uniform heat with the warmest surfaces beneath your feet reducing the likelihood of condensation and mould. There are no fans to create noise and the room is draught free. The water in a hydronic system is totally separate from the domestic water supply so there is no risk of contamination. The pipes are laid with spacings around 200mm, and the house is divided up into zones. Each zone is a length of pipe limited to around 150 metres (about 30 square metres of floor area) - hence a typical property may have six or eight zones -all these pipes are brought together at a manifold which is best placed near the centre of the house to minimise pipe runs. Note that the concrete slab should be left to cure for at least four months before the underfloor heating system is turned on.

Commissioning the system: when an underfloor heating system is used for the first time, the floor temperature must be raised slowly to avoid stress and cracking the slab due to drying out too quickly. The heating system must not be used to cure the slab. A recommendation when commissioning (European Standard), is to use a flow temperature of 20°C to 25°C for three days, then increase by 5°C every 24 hours until the design flow temperature is reached, maintain this for four days then switch off. As the best temperature with a hot water heat pump is around 30°C.

Already have pipes in the floor?

For those people lucky enough to have pipes in the floor already consider fitting a hot water heat pump in place of your existing heating unit.  For a 160sq meter home we would recommend a 11.9 kW Hot Water Heat Pump at approximately $4000.00. Work out how much it's costing you now and give us a call.

However, realize that underfloor heating is not suitable for cooling in summer - we would suggest that a standard high wall heat pump is installed in the main living area for this purpose. This will have the added advantage of providing heat for those sudden cold snaps (underfloor heating doesn't have a quick response time), but this unit doesn't need to be a big or expensive.

Combining under floor heating and hot water heating with one outdoor unit?

Underfloor heating requires large amounts of water at around 30 degrees - a hot water cylinder requires relatively small amounts of water at around 55 degrees.

At these two temperatures a hot water heat pump has different efficiencies, basically the efficiency of a heat pump is lower when trying to get water to higher temperatures. To maintain efficiency it is essential that water for underfloor heating is not taken up to high temperatures and then lowered down.

With our "full flow" technology we can maintain full efficiency for both applications, so that the underfloor heating system will typically be at least 5:1 efficient, and the water heating up to 4:1. With 30 degree water going to the floor, and 55 or 60 degree water to the cylinder - the cylinder itself is only heated when the underfloor is switched off, but a 280 litre cylinder can usually be recovered in something like an hour.

An additional heat exchanger and circulating pump plus some electrical components are required at a cost to supply and install around $1500. Please note these additional components can be fitted to ANY hot size, type and make of hot water cylinder. As an additional heat pump for heating water is $3-4000 the savings are significant. 

Also note these extra items for water heating will probably save as much energy and electricity costs as a solar system costing $5-6000!

In all cases a standard hot water cylinder is fitted with the element, in the unlikely event of heat pump failure you will still have hot water.

Click on the link for a schematic of the combined underfloor and water heating.

How much will this cost?

The typical cost for a 200sq metre home is $16000.00. This is for a underfloor and hot water heating system, up and running. Inclusive of a $2000.00 allowance for a hot water cylinder.

There are six main parts to an underfloor heating system.

• The pipes in the slab
• Prepiping & pre wiring
• The outdoor unit
• Hot water heating kit
• Hot water cylinder
• Supplying and installing a manifold, expansion vessel, circulating pump, bleed valves, connecting pipes, electrics, gauges, commissioning the system etc.

Our knowledgeable and friendly staff are reading and waiting to discuss with you your underfloor heating systems, and any other ideas or questions you have regarding heating for homes. Give us a call today!