Annual Report 2013

Annual Report 2013

Sustainable Home 11 Hollyford Place, Aotea, Porirua

It has now been over two years since we turned on the sustainable features of our new home in the Fjord block of Aotea. During the first two years of use the systems have been bedding in and have been fine-tuned and we are pleased that our fervour for sustainability has been vindicated with the initial results being very encouraging.

Over the two years we have had numerous people who have visited to see and talk to us about the features that we have installed and to get a feel for how sustainability might help them in their own house planning. While there is a lot of recognition of the value of sustainability especially in providing healthy living and wellbeing the number of other homes in the region which have picked up on the sustainability features is small.

Our key driver for building a sustainable eco-friendly home was reinforced by the proven technology that is being used by the Department of Conservation and our understanding of how a sustainable home would not just save us money in the long term but also improve our health and wellbeing as we headed into a relaxed retirement.

The home was finished in December 2011 after going through the design and build process which included educating our design architect and builder on the sustainable technologies that are available. The house was designed and built by Hayward Homes Limited who as a result of the experience gained with our build now promote themselves as a “Sustainable Home” designer and builder for Wellington.

This report comments on how each of the key systems are functioning, the results and the costs and benefits.

 

The Key Features

The two key features in the house reported on below are:  

•         Digital Self Heating Home system (Energy Efficient Homes Ltd)

•         Photovoltaic system connected to - Meridian Energy (Powersmart)

There is also an update on the other features being;

•         uPVC windows and doors (Weathertight Windows and Doors Ltd)

•         LED lighting throughout (Lighting Direct)

•         Water collection and recycling systems (Watersmart)

•         Polished concrete floors (Husqvarna system)

The Digital Self Heating System (DSHH).

The DSHH system provided by Energy Efficient Homes Ltd uses the sun in a solar water system to heat water. There are two arrays on our roof one of which provides our hot water heating for the house, the second providing the hot water for the thermal mass system.

The thermal mass system uses the solar system to heat water which is then heats the ground below the floor slab. The heat is captured in the soil and a layer of core sand between the foundations of the house and below the floor slab producing 248 cubic metres of thermal mass as our core heat source. The foundations are deeper than normal to provide the thermal mass area, and hence the foundations are wider than normal giving the ability to increase the insulation on the outer walls. Two layers of 3.2 Batts insulation were used on all outer walls increasing the thermal seal of the house. The core is separated from the foundations and the floor slab by 30cm of polystyrene. The core over a five year period will eventually have a thermal mass temperature of between 45 – 55 degrees C and it is this heat that is then put back into the floor slab during cold periods to keep the house in a range of 20 -23 degrees.

By the end of this summer the core temperature should be around 34C, however this is dependent on the type of summer we have had. With this summer being one of the poorest on record we are likely to be a little behind that temperature. At the time of writing this report the core is at 30C.

The system was turned on in January 2012 and during the first few months the core which started out at ground temperature of 14C, peaked at 23C. This moved down to 19C over winter. By the end of the first full year the system had reached 24C and by the end of year two this was at 28C. We expect the system will be around 32C by the end of this summer, well on track to reach 45C within the first five years at which time the system will be fully operational and no supplementary power will be required for heating during winter.

In our first winter the house temperature never went below 17C and last winter it was always above 19C which made for a very cosy winter even during the long power outages caused by the winter storms. About 13% of annual power usage in a normal house is taken up in heating the home and once we get the core up to heat winter heating will be zero for our house.

During the first two winters we have used supplementary electric heating to keep the internal temperature of the house above 19C and this is clearly noted in the power usage section of this report. The amount of supplementary heating is expected to decline in the next few years down to zero by the winter of year 6 (2018).

Water heating is normally 33% of power requirements in a standard house and in our case this comes predominately from the sun, a significant power saving for the house. The solar panels heat our hot water for house use and this is stored in a 280 litre cylinder. The system has worked as expected during the year with no issues.

 

The Photovoltaic System

The photovoltaic system (Powersmart Ltd) is designed to provide a maximum of 2.09kw per hour, and is connected through an inverter direct to Meridian Energy. Meridian receive any excess power generated during the day and this power is credited to our account on a 1:1 basis up to 5kWhr per day and then at a reduced rate.

In the first 11 months we generated 2.613MWhr’s of power from the system and in the 2013 year we generated a further 2.952MWhrs giving a total of 5.57MWhr’s for 2012/2013.  Of this 2.323MWhr’s was provided to Meridian and 3.2472MWhr’s used directly by the house.

The best month for 2013 was in January with 369kWhr’s produced for the month an average of 11.9kWhr’s per day and the lowest month was June with 105kWhr’s or 3.5kWhr’s per day. The results show that we had less sun than normal through winter and autumn in 2013 compared with 2012.

The chart shows the monthly cycle with the peaks and troughs around the longest and shortest days.

The amount of power provided to Meridian is impacted during the winter months as the thermal heat in the core for the house takes up to five years to get to a fully sustainable heat. In the meantime we are supplementing with electric heating during the four months of winter. In future years this will not be required. Overall I’ve estimated that in the first two years the system generated around 38% of our power requirement, not bad given the poor winter that we had and the three major power outages during the year. Once the core gets up to heat I expect we will provide about 60% of our power requirements each year.

The Meridian power usage in the winter months shows the supplementary electric heating we had to use over the winter period while the core temperature builds up.

                    

An average house is estimated by the power industry to use in excess of 10MWhr’s per annum. In our case we have averaged just over 7MWhr’s per annum in our first two years and around 40% of this was produced by our photo voltaic system.

Once the thermal core of the house gets to temperature we expect that the house usage will reduce to about 4.5MWhr’s per annum about half the power usage of a normal house, and with our PV system producing about 3MWhr’s per annum around 60% of our power requirements will be provided by our system. At this time our house will be running significantly more efficiently than a standard house.

Other Features Updated:

LED Lighting

We made the decision early on that the house would be lit by LED. There are significant advantages to LED. They run cold and hence can be fully covered in the ceiling by insulation, maximising the thermal seal of the house, they run at about one sixth of the power compared with other light systems and they have very long life. We had a very strong relationship with Lighting Direct who provided a very sharp price for the LED lights and fittings throughout the house.

If we had installed halogen we would have had the equivalent of 5.6kW of lights compared with the 800W of LED light that we have installed. That is a significant reduction in running cost for LED given that lighting is normally 12% of power usage. The LED’s are specified to run for 50,000 hours. I’ve worked that out to mean that we will not replace any lights in our life time even if we live to a hundred.

The lights have been great with no failures and no issues.

uPVC Windows and Doors.

Our windows and doors are double glazed uPVC. Our uPVC system is a Belgium design specifically for the southern hemisphere, and came to us via Australia and was installed by a Dunedin company Weathertight Windows and Doors Ltd for the same price as aluminium.

The only door that wasn’t uPVC was the front door. This door was a standard wooden door, however due to thermal leaks around the door experienced in winter and during southerlies, this door has been replaced during the year with a uPVC door. The change in thermal seal is amazing and heat loss that occurred last winter will no longer occur.

uPVC has the best environmental rating of all systems with double the star rating compared with aluminium. The biggest advantage is no condensation and no heat loss using uPVC.

Water Collection and Reticulation

Our water collection and reticulation systems are both from Watersmart NZ Ltd. The system consists of a 5000 litre tank, buried in our front lawn, that collects rain water of the roof. This water is used for the toilets and for all outdoor taps. It means that during the recent drought we had plenty of water, however with a ban on, it didn’t seem proper to utilise the water we had collected.

We also have a grey water irrigation system which collects water from the two bathroom showers, bath and basins and send this under pressure to our lawn and front garden area. This meant that watering the lawn and garden was always easy, as it happened every time we had a shower.

Both systems are operating as expected with no issues.

Concrete Polished Floors

All hard floor areas are polished concrete using the Husqvarna process. This includes the wet areas, (bathrooms, toilets and laundry) and the entrance hall and kitchen. We had some minor cracking in the concrete which appeared as part of the curing process. This was left for a year to ensure no other movement and all of the cracks have now been resealed and there have been no further problems and all of the floors have survived the earthquakes this year with no problems.

Cost Benefit revisited.

I can compare the cost of the house with and without the sustainable and environmental features. When we started I thought the cost of sustainable features would be about 15% of the normal build costs, but I was surprised to find that the total additional cost for the features comes in at only 8.6% compared with a house without these features. I have used the additional cost between our system and what a normal house would have used in each calculation.

The two main systems are the Digital Self Heating Home and the Photo Voltaic systems, with most other features being secondary to those two systems. The payback period for the full system (not including the water systems) is about 15 years at current power prices, however the price of power continues to increase and the actual payback period is likely to be less.

We have not tried to put a value on the health and wellbeing benefits. Since we have been in the house the temperature has not gone below 17 degrees in any of the rooms and once the DSHH system is fully operational shouldn’t go below 20 degrees. The humidity in the house is also lower than a standard house and these two factors alone make for a consistently warm, pleasant and enjoyable environment. It is a great house to come home to and the warmth on a cold winter’s day is still a joy to experience when you walk in the door.

The house has been assessed by a Real Estate agent and the sustainable features are considered to add considerable value to the underlying value of the property. We are here for the long haul so this part will not be tested for some years to come. However all of the systems are guaranteed for greater than 20 years and should still be in good working condition in the later part of the century.

Our commitment to sustainability has been further reinforced and strengthened by our own experience and we would encourage anyone considering a sustainable home to take the plunge and enjoy the experience you will have.