It has now been seven years since we turned on the sustainable features
of our new home in the Fjord block of Aotea, New Zealand
Changes to the system:
At the start of 2018 (January) we installed a further 12 solar panels
and a 10kwhr LGC powerwall to the photo voltaic system giving a considerable
boost to the solar capacity which is now capable of delivering a maximum
4.67kwp each hour. With the new system in place we can get through most months
with just the solar power and powerwall backup at night.
In late 2017 we also increased the number of panel arrays on the DSHH
system and the two new banks of water heating panels have the new panel version
installed. This has increased the capacity and reduced the time for heating the
system. The maximum core temperature is still about the same but during winter
months there is now more capacity to keep the floor slab at the desired
temperature without supplementing from the core.
We continue to be pleased that our fervour for sustainability has been
vindicated with the results being very encouraging.
The System:
Over the seven 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
years, the reduction in price, especially solar panels and the options for home
owners has certainly increased. More building companies are now offering
sustainable products as part of their build options.
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), expanded in
late 2017 with two further sets of panels.
• 11 panel Photovoltaic system (Powersmart) expanded
to 23 PV panels and a LGC 10kwhr Powerwall (Harrisons) in January 2018.
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 has steadily increased its thermal mass temperature as the
ground under the house has been dried out and sits between 32 – 36 degrees C at
the height of summer 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 the last few years we have realised
that our main issue with the system is caused by the wind which comes from the
north west and as we have a large bank in front of the house this acts as a
ventura effect increasing the ability of the wind to rattle and lift the panels
which over time impacts on the joints for the panels and loosens the
connectors. With this in mind we have started a programme of tightening the
connectors after spring each year.
During the summer of 2017/18 the core
temperature reached 35C, and this dropped to 21C by the end of July as May and
June were unusually cold months.
About 13% of annual power usage in a normal house is taken up in heating
the home and with our system, and especially with the powerwall installed winter
heating should be kept to a minimum for our house.
During the winter period we use 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 has significantly decreased with the inclusion of the
extra PV panels and the powerwall which supplements early evening heating.
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) was designed to provide a maximum of 2.09kw per hour, this was increased
to 4.67kw per hour in January 2018 with the addition of 22 further panels Harrisons) and is connected through an
inverter direct to Meridian Energy. Meridian receive any excess power generated
during the day and while this power was credited in 2012 on a 1:1 basis up to
5kWhr per day this is now credited at just under 8c per unit.
In the last 12 months we have generated over 5.4MWhrs of power from the system of
which we used just over 3.3MWhrs and distributed 2.1MWhrs to Meridian. After 7
years we have generated 22.5MWhrs of which we have used 12.6MWhrs and
distributed 9.8MWhrs.
Over the last year we have been 80% sustainable – amount of power generated
by the system compared with total power used. This is up from 40% in previous
years.
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 both for total power used and
power from Meridian.
An average house is estimated by the power
industry to use in excess of 10MWhr’s per annum. In our case in the last two
years we have averaged 6.7MWhr’s per annum and in the 2018 year 80% of this
power was generated through the PV system.
In 2012 the power cost was 23.19c per unit and
in 2018 it is 29.95c per unit an increase of 29% over the seven years. During
the 2017 year we saved about $1475 in power costs compared with an average house
and in 2018 this went up to a saving of $2260. (see payback section at end of
this report).
Other Features Updated:
LED Lighting
The house is fully lit by LED and after seven years we have had no light
failures. 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.
This year we had the windows maintained by Weathertight Window and Doors Ltd as
some window handles were starting to seize up. The only other issue we have had
is with the door handles where there has been discolouring of the key plastic
panel and some chipping off the bottom of the outside handles. Otherwise all
windows and doors are working well.
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.
During the last few years the pump in the 5000 litre tank had to be
replaced and we upgraded to a more robust model. This summer the pump for the
grey water system also failed and was replaced with a Bosch pump which should
last considerably longer.
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 in the first year 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 years 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. With the price of power continuing to increase the actual payback
period for the original system is now about 11 years and reducing each year.
The additional panels and powerwall have a
payback period of around 11 years as well.
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 tends to stay around 20 degrees during
most of winter. 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. 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.
