Fabric Improvements for Energy Efficiency in ... - Historic Scotland

Fabric improvements for energy efficiency in traditional buildings
Blinds, Curtains and Shutters
Traditional options for reducing heat loss from windows, such as blinds, curtains
and shutters, can result in significant reductions in heat loss with no impact on
window fabric (see Table 1). A combination of these systems can reduce heat loss
by as much as 62%, only 1% less than through the installation of secondary glazing.
While this will result in reduced light levels, the lowest external air temperatures
and period of greatest occupancy (and therefore heat loss) is generally at night.
Roller Blinds. Roller blinds were commonly fitted to windows in the 19th century,
and in many buildings the original brass fittings are still present in the top corner
of the sash case. These blinds (Fig. 18) allow privacy during the day, reduced
penetration of sunlight, and also retained heat. If original fittings remain these
can be re-used with new fabric; alternatively, new roller blind mechanisms can
be installed with no damage to the existing window fabric, in a range of modern
materials with varying thermal or reflective properties.
Curtains. Full length, lined and well-fitted curtains can control draughts and
reduce heat loss by up to 14%. Curtains have no impact on existing window fabric,
although care should be taken to ensure they do not obstruct radiators.
Shutters. Commonly found in older buildings, timber shutters can reduce heat loss
of windows by up to 51% (see Table 1). Due to cost however, many rural buildings
and later tenements were not constructed with shutters and have imitation fielded
panels made to look like shutters. Restoring painted-up shutters is generally
straightforward; the benefits are considerable as thermal imaging can reveal
(Fig. 19). The thermal performance can be further improved through applying
a thin layer of aerogel blanket, resulting in a 60% reduction in heat loss in trials.
Such insulation can be fixed to the internal panels of the shutters, and overlain
with a thin layer of plywood and new beads before painting.
Where shutters have been removed but the framing and housing remains, a new
shutter can be made using either traditional joinery techniques (i.e. mortice and
tenon joints with fielded panels) or by cheaper and quicker modern techniques
(see Historic Scotland Inform Guide: Timber Window Shutters). If there is no housing
or shutter case, a shutter can be fixed directly to the sash case, as sometimes seen
in basements and working areas of older buildings.
If new shutters are being manufactured then they could be glazed (Fig. 20) to allow
them to be closed during daylight hours; in effect acting like secondary glazing but
with the flexibility of a shutter. Such a solution could be particularly beneficial in
commercial properties, which are occupied during daylight hours.
Fig 18 Traditional pattern roller
blinds can result in significant
reductions in heat loss.
Fig 19 Thermal image showing
the benefits of shutters. Image
by Changeworks.
Fig 20 Glazed shutters in use.
18 19 20
15