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Burning fossil fuels to heat water and to keep warm at home is one of the
biggest sources of CO2 in the UK (and other places with cold
weather). This is a much harder problem to crack than greening our electricity
Until recently, we have heated the house and the hot water from a rather old-fashioned
gas boiler behind a gas fire in the living room. From the point of view of CO2 emissions, gas is better
than coal or oil (because it contains more hydrogen and less carbon). But we are
keen to eliminate 'fossil' CO2 emissions altogether, if possible.
We have now improved efficiency by
installing a modern condensing boiler and we estimate that this change has
reduced our emissions of CO2 from domestic heating by about 30% (see
our spreadsheet of
CO2 emissions and savings). This is a
very welcome saving but it would be nice if we could avoid burning fossil fuels
The main options that we are looking at are described in the following subsections (CHP is one
option but this has already been discussed briefly here).
Links:The Renewable Energy Centre
One option is simply to live in a cold house and not use hot water. Some
people do this but it might be difficult to persuade large
numbers of people to give up the comfort they have become used to. In any case,
Britain has a scandalous record for the number of old people that die of
Living in a cold house would be a lot more attractive if there were good
lines in heated clothing. Some motorcyclists keep warm in jackets or trousers
(or both) that are heated safely by low-voltage current from the motor-cycle
battery. With nice designs and improvements in the technology, something like
this could be an attractive alternative to heating the whole house. Given a
supply of electricity that is totally green (as described above),
there would be zero emissions of CO2.
In principle, it is possible to insulate one's house so well that heat from
lighting, cooking and body heat, together with solar energy, is enough to maintain a comfortable temperature
(see, for example, Bed Zed).
Heat exchangers are normally needed to maintain fresh air and conserve heat at the same
Super insulation is much easier to do with a purpose-built house. However, we
think it should be instructive to see what can be done with our bog-standard chalet-bungalow, built in
the 1960s when fossil fuels were cheap and climate change was barely heard of.
We already have rock-wool cavity wall insulation and there is some insulation
in the roof. But something radical is probably needed to make a big cut in
heating. This probably means external insulation. Putting thick layers of
insulation on the inside uses up valuable living space and it is liable to leave
cold spots. External insulation has the advantage that the walls act as a heat
Here are some of the problems we anticipate in retrofitting super insulation
to the outside of a house like ours:
- If we were to add external insulation of the sort of thickness that is
used in the demonstration building at the Centre for Alternative Technology - about 1 metre - then there would be
very little left of the paths around the house. This would not matter at the
back and front but on each side, our neighbours' fences prevent us taking any
more space. We could only manage insulation up to about 300 mm at the sides. An interesting development in this connection is the use of insulation panels from which air has been evacuted (see Vacuum Insulation). Apparently, this increases the level of insulation quite substantially which means that thinner insulation panels may be used.
- This kind of insulation would alter the appearance of the building
substantially. It is likely that this would cause problems with existing
planning regulations and practices, which are rather conservative. The Government needs to ensure that
planning authorities will not prevent this kind of insulation being added to
existing buildings, with possible exceptions for buildings with special
- We would anticipate adding one or two additional layers of glazing to each
window at the level of the new external face of the wall resulting from the
addition of insulation. We have not so far been able to discover any commercial system that will
solve this problem.
- Because our roof space contains rooms, it is not possible to add thick layers
of insulation in the way that would be possible if the loft space were empty.
There is some insulation between the ceiling and the tiles but there is a limit
to what can be put in there. If we are to achieve super insulation, we probably
need some kind of external cladding that can be laid on top of the existing
roof or we would have to remove the tiles, lay insulation on top of the beams
and fix the tiles to the insulation. We have not so far been able to discover any commercial system that will
solve this problem.
- While it should be possible to add insulation under the ground floor where
there are suspended floors, some of our ground-floor rooms have solid floors
and insulation could only be added by removing the concrete..
In general, there is a need for
'systems' that can be retrofitted in a flexible way to existing houses of many
different designs. We believe the Government should take steps to ensure that
systems of this kind are developed and made available for purchase by individual
If the stock of existing houses in
the UK is to be
insulated up to the standards that are now needed, the Government will need to
provide very large subsidies to bring down the cost to individual householders.
Links: Old Home SuperHome, Webcast about the passive house concept from Leonardo Energy, Passive House Solutions Ltd, Vacuum Insulation, Passive House Institute, PassivHausUK, Permarock, Sto
external wall insulation, Envirowall, Thermafleece, INCA, KnaufInsulation, Roofing Solutions UK.
Burning fuels derived from plants means that there is no net release of CO2.
Possible fuels include logs, wood chips, wood pellets (see below), agricultural waste, biogas,
biodiesel and vegetable oil (see below), and
newspaper briquettes. Although peat originates from plants, it is really a
fossil fuel and there are other environmental reasons not to destroy yet more
A particular problem with biogas is that it
cannot be liquefied like LPG. It can be stored under pressure but this is
cumbersome and not entirely safe. Consequently, it does not look like a good
option for domestic heating. That said, we are interested in the Greenfinch
Biowaste Digester, generating biogas (methane) from
kitchen waste and the like.
For biofuels to be truly green, it is necessary for them to be produced and
transported with zero CO2 emissions.
If biofuels are to be adopted for
domestic heating, they will need to be as cheap as fossil fuels or cheaper.
Costs of biofuels compared with conventional
Links: Rika Stoves (pellet
It is possible to move heat from the outside of a house to the inside using a
heat pump that works like a fridge in reverse. The heat can come from the air or
from pipes buried in the ground.
If the pump is run on green electricity or something like biodiesel, then
zero net CO2 emissions can be achieved. The main attraction of heat
pumps is that the amount of energy needed to move heat from one place to another
is relatively small compared with the energy in the heat itself (about 1:4).
This is all proven technology and sounds attractive but there are few suppliers
of heat pumps for domestic use in the UK.
Although some installations attract
VAT at 5% (compared with the normal 17.5%), there is a need for the market to be
given additional encouragement by tax incentives and/or grants.
Pump Association (UK), UK Heat Pump
Solar water heating and passive solar heating
Solar water heating
In the summer of 2005 we arranged for a Solartwin solar water heater to be installed. This is a neat design that is significantly
simpler than some other systems. It is designed so that freezing causes no
damage and it includes an electric pump powered by a small photovoltaic solar
panel so that there is no need to use mains electricity which may have come from
A grant of £400 from clearskies meant that the net cost to us was about £2,200. The panel is mounted on a roof
that faces south-west, which is not quite as good as due south but apparently
gives 95% of what one would expect to get if it did face due south.
We are very pleased with this device. Most of the time we do not use the gas
boiler to heat the water. During the summer, we get quite a lot of hot water,
mainly when there is direct sunshine. When there is direct sunshine during the
winter, the water is heated to a pleasantly warm temperature which is quite
suitable for many purposes: washing one's hands, washing dishes, cleaning floors
etc. If we need water that is hotter, then we use the gas boiler for a short
time to give just enough hot water for what we need.
Passive solar heating
Passive solar heating works best when a house has been purpose-built to take
advantage of the sun. With an existing building, it is possible to get some
solar heating from a conservatory or from areas of glass covering south-facing
walls or roof or both.
Electricity generated inefficiently from fossil fuels or dangerously from
nuclear power is a poor option for domestic heating. But electricity from wind
power or other renewable resources is worth considering. At present, it is
rather expensive for space heating or water heating but this may change.
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