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Underfloor Heating Cost Comparisons

Advantages of cost comparisons

The purpose of this guide is to show the cost comparisons between the various types of available underfloor heating methods. Each system has its benefits in terms of efficiency and costs. All cost estimates are excluding GST. Please refer to our website www.centralheating.co.nz for more information on underfloor heating.

Kiwi InslabThis is the most common warm water underfloor heating system installed in NZ because it is the most cost effective to install in a standard home with a concrete floor slab. Because existing homes already have a slab in place, the Kiwi Inslab method is only possible in new homes or during extensive renovations.

Although the heating system installer will install the pipes in the floor, the Kiwi Inslab method requires special considerations from the builder as well. The builder will need to supply and install polystyrene underneath the slab for added insulation and mark out the locations of the walls on the polystyrene. RibRaft and other pod floors have polystyrene insulation as part of their construction, so the builder does not have to allow for polystyrene when these floors are used. The engineer may specify a thicker

concrete slab, sometimes an extra 25mm thick, to accommodate the pipes. A typical Kiwi Inslab system will provide heating to the room in around eight hours and is generally left on low continuously.

Although these systems work very well, around 10-15% of the heat can leak from the slab edge and through the foundations. There are methods of insulating against this, but there is a general reluctance in the construction industry to implement them due to time and cost restrictions.

Kiwi Inslab Per SQM

50mm Poly* $10.00

Install Poly* $1.50

Marking Out Walls $0.50

Edge Insulation Method** $6.00

Increase Concrete*** $6.00

Install Concrete $-

Pipe 150mm Spacing $12.00

Install Pipe $6.00

$42.00

* Deduct if RibRaft/Pod floor construction ** If possible (per SQM) *** Additional 25mm of concrete may be required

Kiwi Inslab

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European Screed Per SQM

Poly 35mm $8.00

Adhesive $0.50

Edge Insulation (per SQM) $2.00

Install Poly & Edge (per SQM) $1.50

Pipe 150mm Spacing $12.00

Install Pipe $6.00

Screed $20.00

Install Screed $12.00

$62.00

European Screed Floor

VarioComp Per SQM

Pipe Panel $49.00

Edge Insulation (per SQM) $2.00

Install Panel $12.00

Pipe 100mm spacing $22.00

Install pipe $6.00

Screed $13.00

Install screed $8.00

$112.00

VarioComp

European Screed FloorThis is the most common method throughout the rest of the world for warm water central heating in residential buildings. Unlike the Kiwi Inslab method, it is possible to install screed (a type of concrete) in an existing home, but because it requires major renovation and a loss of room height (85mm), it is generally installed in new homes.

In this method, the pipes are clipped to polystyrene, which sits on top of the construction slab of the house. A 50mm screed of cement mix is laid on the polystyrene. Edge insulation assists in reducing energy loss from the heated screed. The lower thermal mass of the thinner heated floor means the reaction time of the floor is faster than the Kiwi Inslab method, although it will still take four or more hours to respond.

VarioCompVarioComp is a system by Variotherm in Austria. It is a quick-reaction, light-weight underfloor system that can be used in both new and existing houses. It can be installed on a concrete or wooden floor either directly or on a thin layer of polystyrene. The pipes used in the system are smaller in diameter than what is used in other methods. These pipes are installed in a reinforced gypsum board panel or polystyrene, and covered with a filler compound, which is then levelled for the floor coverings.

This system has the highest efficiency as the pipes are normally spaced at 100mm centres (typically the other methods space the pipes at 150-200mm, which requires higher water temperature for the same output). This enables the heat source powering the system to operate at a very low temperature, which is ideal for renewable energy systems. The total height of the VarioComp is 20mm (without polystyrene) making it perfect for retrofitting in existing buildings or in very thermally efficient new buildings.

SummaryWhile each system has its advantages, floor coverings, insulation and glazing play a huge part in making a system efficient, effective and with reasonable running costs. For all of these methods of warm

If Insulation Required Per SQM

High Density Insulation (10-20mm) $8.00

Install Insulation $4.00

If Carpet or Lino Floor Covering Per SQM

Levelling Compound (5mm) $26.00

Install Levelling Compound $16.00

water underfloor system, the comfort in a house is unrivalled when you choose a system designed and supplied by Central Heating New Zealand Ltd.