Here in the UK there
is a lot in the news about soaring energy costs and the discomfort and risk to
people who cannot afford to heat their homes adequately. Having had over fifty years’ experience, in a professional capacity, of
trying to provide suitable internal environments for people in buildings I thought I would
try to offer something useful by way of guidance on the subject.
In what follows I have
tried to explain things in layman’s terms.
First, let us consider the factors affecting human’s thermal
comfort. These personal factors are:-
·
Metabolism
(all the chemical factors in a human being that result in energy production). In this respect we are all different.
·
Amount
and type of clothing. Another area where
we are all different!
So doing some fairly
vigorous exercise before going to bed will mean you will slide between the
sheets feeling warm, whereas sitting around all evening watching the TV will
lower your metabolic rate and mean that you go to bed feeling cold.
Similarly wearing warmer
clothing which reduces the natural heat loss from your body will result in your
feeling warmer. People in bygone days
realised this and that is why nightcaps and bed socks were popular in unheated
bedrooms in draughty houses. I wish I
could get my wife to wear bed socks, instead she prefers warming her feet up on
my legs!
Then there are the
environmental factors:-
·
Air
temperature
·
The
surrounding surface temperature of walls, floors, ceilings and glazing
·
Air
movement (velocity)
·
Relative
humidity (in winter when internal relative humidity is generally low this does
not have a significant effect so we will ignore it)
If the air temperature
around your body is below your body’s surface temperature your body will lose
heat to the air and you will feel cooler.
If the surfaces around you are colder than your skin surface temperature
your body will radiate heat to those surfaces and you will feel cooler. If air is moving over your bare skin then it
will evaporate moisture from your skin and for this evaporation to take place
energy is required and the energy comes from your body making it feel colder. You can prove this evaporation effect for
yourself by licking the back of your hand and then blowing across the licked
area. You will feel it go cold and your
body will then have to warm it up again.
The heat to warm your skin up has to come from your body.
Hopefully what we have
looked at above is second nature to you and you dress appropriately keeping
body parts covered (insulated) and you might consider wearing bed socks or even
a night cap if your bedroom is cold at night.
Now let us look at the
environmental factors, but before we do we must consider the two ways in which
heat is lost from a room.
·
If
there is a temperature difference across a room surface (say a wall with 1 deg
C outside and 21 deg C inside) then heat will want to flow from the warm side
to the cold side. We call this a “fabric
loss” because heat is flowing through the fabric of the room. We insulate walls, ceilings and floors to
make it harder for the heat to flow through them. We double glaze windows for the same reason.
·
If
a wind or breeze hits an obstruction it results in high pressure on one side of
the obstruction and low pressure on the downwind side. If there is an air
pressure difference across a room (or a building) due to a breeze or wind then
the high pressure air tries to reach the low pressure air by flowing round the
obstruction or through it. We call the
effect in the room a draught! The effect
of the room air being changed by draughts is very significant in terms of heat
loss particularly in older buildings when in windy conditions the whole volume
of room air may be changed one or even two times per hour. All of this air has to be heated up to room
temperature in order to maintain that temperature and the required comfort
level. Also if there is a lot of air
movement in a room due to draughts the occupants will feel cooler.
Given all of the above
what are the practical ways available to help maintain comfort whilst reducing
energy bills?
In terms of reducing
the “fabric loss” the straightforward ones are:-
1. Insulate the room/building surfaces
with cavity and roof insulation or surface insulation if a solid wall.
2.
Use
heavy curtains, preferably from floor to ceiling and keep them closed when
possible. Close blinds especially at
night.
3.
Insulate
behind radiators with foil faced polystyrene sheets.
4.
Insulate
the floor with thick carpets and underlay.
5.
Turn
off radiators in parts of the home that are unoccupied or if radiators are
fitted with thermostatic radiator valves reduce the setting. Shut the doors to these areas.
6.
I
was always being asked which is best: do you turn your heating off when not
required or is it better to keep it running continuously. In terms of saving energy you should turn it
off (preferably onto a frost protection setting so you don’t get frozen pipes). Common practice, especially if you have young
children, who kick their bed clothes off, is to turn the thermostat down at
night or if you have a two zone system, only keep the bedroom zone running at
night.
7. Warm air systems involving fans,
heater batteries, ducts and grilles will heat up a home quicker than water
systems so the pre heat period is shorter but they do result in more air
movement so room temperatures usually need to be slightly higher than for a
radiator system which does not have increased air velocities. Make sure the vanes on the grilles direct the
warm air down otherwise you will have cosy temperatures at ceiling levels
whilst being cold in the occupied area.
Regarding controlling
infiltration a balance has to be struck between health and safety issues and
controlling energy costs. Even if it
were possible to eliminate air movement from outside completely it would not be
desirable. Room occupants require oxygen
to breath and the dilution of the carbon dioxide they breath out. Both require some fresh air entering the
space. If the room is being warmed by a
heat source that involves combustion actually in the room such as a gas fire,
oil fired heater or even a multi fuel heater it is crucial that adequate fresh
air ventilation to the room or appliance is provided. So don’t go blocking off vents specifically
provided for combustion air supply. To reduce
ventilation for combustion can result in the appliance producing a deadly gas
called carbon monoxide. This colourless,
tasteless and odourless gas makes one feel happy as a prelude to
unconsciousness and death as it restricts the flow of oxygen to vital organs.
In terms of reducing
the infiltration loss here are some practical suggestions:-
1. On a breezy cold day check windows,
doors, skirting, etc. for obvious draughts using the back of a damp hand. You will only be able to feel the air coming
in on the windward side of the building, so you need to repeat the exercise
when the wind is blowing from other directions.
Having determined where the draughts are you need to try to block or
restrict the air path using an appropriate method. Some suggested methods are:-
a. For old metal casement windows with
warped frames – clean off the window edges, put a release agent on one surface
(washing up liquid) and a clear silicone sealant on the mating surface and close
the window. Twenty four hours later the
window can be opened again but by then the silicone should have made a perfect
seal. If you forget the release agent
you will probably never get the window open again!
b. Old wood sliding sash windows are
more of a challenge. If you are looking
for a cheap temporary fix, either wipe clean and tape over all the gaps or tape
a polythene sheet over the whole opening.
This is also the way to carry out a temporary fix if the window pane is
broken.
c. Silicone seal any cracks or gaps
around the frame and also check under the window sill.
d. With double glazed units check all
the edge seals are in place and if not replace.
Quality double glazed units usually come with “trickle vents” at the
top. These could be closed during severe
weather conditions but I usually like to see them left open to provide normal
ventilation.
e. Pay particular attention to external
doors, fitting draught strips if necessary and using the old-fashioned fabric
sausages laid along the door bottom to block draughts.
f.
During
windy weather it reduces cold air infiltration of outside air if all internal
doors are kept closed.
g. If you don’t have fitted carpets then
check the gaps under skirting boards. If
you cannot afford or cannot use a sealant gun then fold up strips of newspaper
or card and force the strips into any gaps.
Finally, if you feel your thermostat is set too high, don't suddenly turn it down a couple of degrees, that will only upset other members of the family. Do a staged reduction over a week so they and you can acclimatize.
I expect there are some suggestions I have missed, so please let me know if you think of any.
.JPG)
