Annual Report 2015

Annual Report 2015

Sustainable Home 11 Hollyford Place, Aotea, Porirua

It has now been four years since we turned on the sustainable features of our new home in the Fjord block of Aotea. After four years the systems should be well and truly bedded in, the exception is the Digital Self Heating House system as the core normally takes about 5 seasons to completely dry out and become very good at retaining heat. We continue to be pleased that our fervour for sustainability has been vindicated with the results being very encouraging.

Over the four 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. This has led to other houses in the region being constructed with similar features. 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 still fairly small.

It is encouraging to see the growth in sustainable products over the last four years, the reduction in price, especially solar panels and the options for home owners has certainly increased. This year for the first time we are seeing building companies offering sustainable products as part of their build options.

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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 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 35 – 40 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.

During this year we were pestered with a leak which was very hard to locate and each time the system lost pressure we also lost heat from the core. The leak was finally located in October and was one of the connectors to the solar tubes which sprung a leak but only when it got to a certain temperature. With this fixed we are now hoping that the next year will go a lot smoother, however we are probably a year behind now in drying out the core.

By the end of 2015 we were expecting that the core temperature would be around 34C, however the early part of summer delivered poor weather and by the end of December the core was only 29 degrees, only 1 degree above the 2014 reading.

The system should get into the 35 – 45 degree range 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. Each year the heating of the core improves as the earth below the house is dried out by the stored heat.

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 should be close to zero for our house.

During each of the four winter periods we have used supplementary electric heating to keep the internal temperature of the house around 20C 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 closer 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 continued to work 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, a further 2.952MWhrs during the 2013 year, 2.925MWhrs in 2014 and 2982MWhrs in 2015 giving a total of 11473MWhr’s for the 4 year period. Of the 8.49MWhrs generated, 3.854MWhrs was provided to Meridian and the balance used directly by the house.

January has been the best month each year with around 360kWhr’s produced each time with an average of 11.6kWhr’s per day and the lowest month has been June with 115kWhr’s or 3.8kWhr’s per day.  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.

Since we have started the system has generated around 37% of our power requirement. Once the core gets up to heat I expect we will provide closer to 60% of our power requirements each year.

It is interesting to note the differences in power usage each year. The winter heating supplemented by electricity is clearly seen in the three charts below with higher readings in June, August and October periods (electricity usage is read every two months), but of more interest is the significant reduction in total over the four year period and as the core temperature has increased and stabilised during each summer.

As can be seen in the table below the average KWhr provided by the power company (Meridian) during summer months is significantly different from the winter months. While this is expected given the electricity heating, you can also see that the winter average is coming down as the core temperature slowly increases each year. Once electricity heating is not required the full year average KWhr per month should be closer to that over each summer month.

	Total KWhr Usage	Avge Monthly KWhr	Summer KWhr Usage	Summer Avge Monthly KWhr	Winter KWhr Usage	Winter Avge Monthly KWhr
2012	6390	**581	1612	*322	4778	796
2013	7470	622	1327	221	6143	1024
2014	5606	467	1538	256	4068	678
2015	5317	443	1497	249	3820	636

* 5 months of summer as system not on until February   ** 11 months

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 7.7MWhr’s per annum in our first four years and around 43% of this was produced by our photo voltaic system in the 2015 year. During the four years we have produced over 11MWhr’s of which 5.2MWhr’s has been sent to Meridian the balance of 6.3MWhr’s being used by the house.

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 was replaced during the second year with a uPVC door. The change in thermal seal is amazing and heat loss that occurred during the winter of 2013 has not occurred since.

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 which collects rain water off the roof. This water is used for the toilets and for all outdoor taps. It means that during dry periods we have plenty of water for the garden, however with a ban on, it didn’t seem proper to utilise the water we collect.

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 means that watering the lawn and garden is simplified, as it happened every time we have 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 any earthquakes that occurred during the 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) was originally estimated to be about 15 years at 2012 power prices, however the price of power continues to increase and the actual payback period is now about 13 years and reducing each year.

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.