The owners of the Henderson Home were, quite frankly, fed up with cold draughty homes and ever-increasing power bills. They wanted to invest in a home that provided the comfort they wanted, with minimal power costs. 


They have now been in the home for 12 months. The home has far exceeded their expectations with the high level of health and comfort:  

“Once you have lived in a home like this, it would be a struggle to go back to living in a standard NZ built home.” 

Read on for the full spec description and details on just how this fantastic home achieved its goals. 

The Insulation 

Insulation is a key component for any home, as it adds significant value in keeping the home warm in the winter and cool in the summer.  

The new standards for the NZ Building code from May 2023 increased the insulation values for the roof/ceiling to R6.6 and the walls to R2.0 (Double what the old building code standard was for the ceiling.) In our case study home, the Ceilings are R8.0 and R4.8 in the walls (at double or more the NZ building code standards). This is made up of two layers of R4.0 in the ceilings, one layer of R3.6 in the timber frame wall and a further R1.2.  

The whole house is highly insulated with Terra Lana WOOL insulation for sustainability and performance. Terra Lana wool insulation was used for many reasons, but mainly because it is local, and sustainable and all scraps head back to the factory to be reused. The garage is also highly insulated in the same way, with insulated garage doors.  

Generally, floors have a lot of heat loss, so minimising that was carried out using 150mm insulated panels and polyblock on the foundations. This made it simple to keep the heating or cooling in the floor and maintain the high efficiency of the home. 

The Building Wrap 

The House is entirely wrapped with Pro Clima Intello. This is a building paper which is taped to completely seal the home from draughts or any air from the outside. This provides minimal air changes within the home- so the heat generated within the home stays in the home (and minimal heating is required).   

The outcome is a home that is easier to keep warm, lower energy bills, no draughts, more comfort, a healthier home with less condensation and mould. Mechanical ventilation can be used as well as natural ventilation (doors and windows being open) to achieve the desired comfort in the home.

The Windows 

All windows and doors are triple glazed, thermally broken and argon filled. The windows provide excellent insulation and also allow minimal noise from the outside. The glazing is also set up to minimise UV intrusion into the home. The windows chosen were from E13 Performance Windows 

Triple glazing is gaining traction in NZ, with the energy efficiency provided keeping the home warmer or cooler. The extra pane of glass allows another surface to apply low E coatings to help control the sunlight into the home (which adds excess heat into the rooms). Another important concept can be noise reduction from the outside, keeping the home quieter. “Thermally broken” windows significantly reduce the heat transfer through the window frames creating better efficiency and no condensation forming on the inside of the window joinery. It all adds to the comfort and efficiency of the home. 

The Front door is also thermally broken to minimise heat loss. There was no point having triple glazing if the door was not thermally broken and airtight. E13 Performance Windows took care of that too. 

The Solar Shades 

On the north side of the house there are “solar shades” above the windows. The shades are set to minimise the summer sun getting into the home and overheating but allow maximum sun in the winter to heat the home naturally without heating being required (or at least a smaller amount of heating).  

The Underfloor Heating 

There is underfloor heating in the concrete and tile floor areas and “active ceiling” panels in the bedrooms. The ceiling heating provides a faster reaction time (similar to radiators). High performance homes do not always require a lot of heating. However, with the concrete and tile floors in this home, it adds to the comfort, to take the chill off the floor and maintain a constant warmth in the days of inversion – which can be bone chilling.  

The home has underfloor pipework in all the areas with concrete and tiles. The bedrooms are carpeted and as the rooms barely get below 16 degrees, having the Messana active ceiling panels supplied and designed by Waterware placed in the ceiling, using the giboard ceiling to act as a radiator takes the rooms quickly to the temperature the occupants find most comfortable. The Active ceilings react much quicker than the underfloor, so don’t have the “lag time” to wait. The panels use the warm water from the heat pump to produce the warmth needed in the room. The Active ceiling panels were predominantly put in place for cooling in the summer months, with the heat pump working in reverse to create the perfect sleeping temperature. The concrete floors were also cooled by the heat pump, to maintain a constant comfortable temperature in the hot Central Otago Summers.

The Heating & Hot Water 

All heating and hot water is powered by an air to water heat pump for a renewable energy generation source.  The Stiebel Eltron air to water heat pump has been calculated and sized for the demand of the heating/cooling and hot water of the home, in this case the WPL A07 or 7 kw high temperature heat pump was all that was required.  

The Heat pump can heat the domestic hot water to 75 degrees if required, but for this home the hot water is heated to 50 degrees and topped up every two days to 60 degrees for legionella. The 400L Stiebel Eltron HWC also has a large heat exchanger so the heat pump can heat the hot water quickly and efficiently.  

The heating and cooling water is stored in a buffer tank, so the heat pump only has to provide the energy required for the supply of the buffer tank, keeping the heat pump energy efficient with longer run times, so the compressor/inverter has less on/off cycles.  

The whole heating/cooling system is run using an outside sensor: the heat pump only delivers the heating or cooling needed at any given time of the day. If the outside temperature is -5 and the indoor temperature inside is required to be 22 degrees, then the heat pump is working hard to deliver the temperature difference needed, however, if the outside temperature is 10 degrees and the internal temperature is 22 degrees the heat pump adjusts and compensates for the temperature difference required, delivering a much lower temperature heated water to the underfloor. Most of the time in this home, the buffer tank will run at 30 degrees to maintain the 22 degrees in the living/kitchen area, as the temperature rises outside the buffer tank will run at 25 degrees. It is an extremely efficient and comfortable way to run the heating/cooling system. 


The fire in the home is a Biofuel fire which is flueless (to maintain air tightness of the home) and uses organic plant-based biofuel to operate. Biofuel fires are a relatively new concept to the New Zealand market yet have become quite popular in Europe and other parts of the world that have smoke-controlled zones similar to Central Otago.  

The Biofuel fire chosen was from Naked Flame and produces a surprising amount of heat for the room. Bioethanol is pure alcohol- the combustion of bioethanol is clean, which makes it an efficient and effective source of heat because there is no soot, ash or harmful emissions that need to be extracted through a flue – meaning all the heat stays in your room.  

Bioethanol – or simply ‘ethanol’ is a renewable energy source made by fermenting the sugar and starch components of plant by-products – mainly sugarcane and crops like grain, using yeast. It is also made from corn, potatoes, milk, rice, beetroot and recently grapes, banana and dates depending on the country’s agricultural strength. 


Cooling is also provided by the same heat pump using the underfloor pipework and the ceiling panels. There are days when the home will overheat, and the cooling maintains a comfortable temperature without opening doors and windows. 


The whole house had mechanical heat recovery ventilation. This ventilation provides clean filtered air, helps control some of the temperature in the home, removes moisture from the home to maintain balanced air without the need to open doors and windows. There are two Stiebel Eltron heat recovery ventilation units in the home. This has provided a dust-free environment, with dry, clean fresh air provided at all times. All moisture is removed by the ventilation system from the home.  

The dry environment makes the home easy to heat or cool, and the heat recovery system integrates well with the heating and cooling of the home, without the need to open windows or doors for fresh air. The whole system is designed to be balanced for the supply and extraction of air within the home.  

For cooking, a recirculating range hood has been used to maintain the air balance in the home. To maintain the air balance in the home the range hood is a recirculating model with charcoal filters to extract and food moisture, fats or other cooking emissions before being removed by the ventilation system.


Fire Sprinklers 

For peace of mind, the whole house has fire sprinklers fitted throughout (including the garage). There is a 25000L in-ground water tank which has a designated 7000L of water specifically for the fire sprinklers.  

 The sprinklers are not the sprinklers you would normally see in a commercial building, they are hidden in the ceiling behind small coloured discs. Leap industries provided the design and calculations needed for the home with a simple step by step installation document. This was a “no brainer” for the peace of mind to protect the occupants of the home and to protect the home if the house was unoccupied. Part of the cost was offset by only requiring one water tank for domestic water and firefighting. 


Water Filtration 

All domestic water is filtered and run through UV. The water delivered to the water tank is clean, however, a Davey Microlene Smart UV filtration unit was added to maintain a clean and fresh water supply at all times.