Annual Report
2012
Sustainable
Home 11 Hollyford Place, Aotea, Porirua
It has now been over a year since we turned on
the sustainable features of our new home in the Fjord block of Aotea. During
this the first year of use the systems have been bedded in and fine-tuned and
we are pleased that our fervour for sustainability has been vindicated with the
initial results being very encouraging.
During our first year 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 take up
is slow.
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 each of the key systems
used, the results and the costs and benefits.
The Key Features
The key features in the house and commented on
below are:
•
Digital
Self Heating Home system (Energy
Efficient Homes Ltd)
•
Increased
insulation throughout
•
uPVC
windows and doors (Weathertight Windows
and Doors Ltd)
•
LED
lighting throughout (Lighting Direct)
•
Polished
concrete floors (Husquvarna system)
•
Photovoltaic
system connected to - Meridian Energy (Powersmart)
•
Water
collection and recycling systems (Watersmart)
•
Induction
hobs for cooking (Fisher Paykel)
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 stored 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 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.
During our first year the core which started
out at ground temperature of 14 degrees, quickly moved up to 19 and then 23
degrees in late April 2012. This slowly decreased to 19 degrees and stabilised
at that temperature over winter. During this spring/summer the core built up to
reach 29 degrees and this heat is extracted back for use in the house via the
computer system over this winter to keep the house warm.
We have been told to expect the core to reach a peak of about 35 degrees
next summer and we will get to about 50 degrees by year four. Due to the low
core temperature in the first year we had to supplement the system with
electric heating and you will see this in our power usage report.
In our first winter the house temperature never
went below 17 degrees and a small amount of background electric heating had to
be provided to maintain a minimum 19 degrees in all rooms of the house over
winter. About 13% of power usage in a normal house is taken up in heating the
home and in future years this will be zero for our house.
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. Once the
cylinder is up to heat these panels then supplement the heat going to the
thermal mass core.
The Photovoltaic
System
The photovoltaic system (Powersmart Ltd) provides 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 13 months we generated 3.35MW of power from the system. Of this
1.52MW was provided to Meridian and 1.82MW used directly by the house.
The best month was January this year with 369
kW produced for the month an average of 11.9kW per day and the lowest month was
July with 129 kW.
The best day during the year produced 16.1 kW
and this was in December 2012 close to the longest day when the maximum
available sunlight and when it was at the right angle to the solar panels on
the roof exists. The chart shows the monthly cycle with the peaks and troughs
around the longest and shortest days.
The amount of power provided to Meridian was
impacted during our first winter due to the lack of thermal heat in the core
for the house and the need to supplement with electric heating during the four
months of winter. In future years this will not be required. Overall I’ve
estimated that in this first year the system generated around 50% of our power
requirement, but once the core gets up to heat this will increase to about 75%.
These two daily charts show the difference between a nice autumn day
with steady increase of power during the day and what happens on a dull day
with little sun.
An average house is estimated by the power industry to use in excess of
10MW per annum. In our case we used just over 6MW in this our first year and
around half of this was produced by our photo voltaic system. However once the
thermal core of the house gets to temperature we expect that the house usage
will reduce to about 4.5MW per annum about half the power usage of a normal
house, and with our PV system producing in excess of 3MW per annum around 75% of our power
requirements will be provided by our system.
The Meridian power usage in the four winter months shows the
supplementary electric heating we had to use over the winter in this first year
due to the lack of core temperature.
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 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….
uPVC Windows and Doors.
All 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 alumimium.
uPVC has the best environmental rating with double the star rating compared
with aluminium. You get no condensation and no heat loss using uPVC. The
windows and doors have meet all of our requirements and we have not had any
hint of condensation at all.
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.
Induction Heating
and Concrete Polished Floors
And finally the oven top provides induction
heating which uses magnetic technology to produce heat which is extremely
efficient. All hard floor areas are polished concrete using the Husqvarna
process. This includes the wet areas, (bathrooms, toilets and laundry) and the
entrance way and kitchen. We have some minor cracking in the concrete which is
still being resolved.
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
winters 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.
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