Warmer Bath

Improving the energy efficiency of traditional homes in the City of Bath
Insulation
The traditional homes of Bath were built without
thermal insulation. The only original insulation is stuffed
between the floorboards to reduce the transmission of
noise between floors. The builders of Bath assumed that
winter warmth would be provided by roaring fires; their
focus was on the generation, not the conservation, of
heat. Only now, in the twenty-first century, have these
priorities been reversed.
In any building, most of the heat escapes through the
walls, roof and floor. Insulation does not stop the heat
loss but it does slow it down dramatically. Although
traditional Bath stone walls provide some protection
against the cold, they are by no means ‘warm walls’. Heat
passes through a 300mm limestone wall at about six
times the speed it flows through a modern wall built to
current building standards. Even when they perform at
their very best, traditional homes are cold by modern
standards.
Some parts of traditional homes are, however, a great
deal easier to insulate than others. Your walls may
make up the greatest area of the exposed skin of your
home but the difficulty, cost and risks of insulating solid
walls pushes them to the bottom of the priority list for
insulation. The loft is the place to start, closely followed
by your ground floor.
Loft insulation
Insulating your loft is a highly cost-effective way of
reducing your heat losses as about a quarter of all heat
losses in an unimproved building are through the roof
(though a good deal less in a five storey Georgian house).
It is also a relatively straightforward job in a traditional
building if the loft space is accessible.
Many of the traditional homes of Bath do not,
however, have loft spaces. Mansard roofs are not so
straightforward to insulate. If you have a mansard
roof or a room in the roof, you can install rigid board
insulation in the manner of internal wall insulation (see
page 44). Alternatively, if your mansard roof is in need of
renovation, or you have a loft that you want to convert
to a room, use this opportunity to combine roof renewal
with comprehensive insulation both between and in
front of the sloping rafters.
If you do have a loft and there is already some insulation
up there, it probably is not enough. The recommended
minimum depth is 270mm of mineral wool, fibreglass or
sheep’s wool insulation. Topping up your insulation, or
replacing it if it is old, poorly installed or damp, will make
a noticeable difference to your heat losses. Ideally, lay
insulation both between and across the rafters (if rigid
board insulation is used for the latter, the space is more
easily used for storage once the job is complete).
Many people install loft insulation themselves. Rolling
out insulation between the joists of a loft is a relatively
straightforward job. However there are tricky details
which you need to get right, and which may justify a
professional job. There are two things to pay attention to:
maintaining ventilation to the roof space and ensuring
that there are no gaps which allow the heat to get past
the insulation.
Above the insulation, your loft will be cold in the
winter. Consequently, any water vapour that gets into
the roof space is likely to condense. If the roof space
is not ventilated, this moisture will linger and lead to
potentially serious problems of mould and rot in the
roofing timbers. It is therefore essential that the air above
the insulation is ventilated to the outside. The simplest
way to achieve this is to leave a gap at the eaves – if
you have them. Georgian houses with parapet roofs do
not have open eaves and in such cases you may have
to install special roof tiles with integrated ventilation
holes. If you have open eaves but the thickness of the
insulation blocks them up, install ventilation panels
between the insulation and the rafters (rafter trays or
eaves ventilators) to maintain the air flow from the eaves.
Covering up the entire floor area of the loft is not always
easy. If you have a loft hatch, this must be insulated and
have an effective draught-seal. You may need to install
a new loft hatch to achieve this. If you have a water tank
in your loft, the insulation must be taken up and over it
(if you go under it, the water will freeze in the winter).
Any exposed pipework must also be insulated. Avoid
installing ceiling-recessed downlighters in top rooms
but, if there are any penetrations in the ceiling below
Sheep’s wool insulation laid between the joists of a loft space in a late
Georgian house on Bathwick Hill
43