Small tweaks to the
design of windows can lead to major improvements, lowering space heating costs,
reducing overheating risk and maximising daylight according to the latest guide
from the NHBC Foundation.
Windows - making it clear, Energy, daylighting and
thermal comfort offers new analysis to help designers optimise their
window design.
The results were
modelled using the 'Passivhaus Planning Package'; specialist software designed
to provide sophisticated analysis of energy use and comfort within homes.
Researchers looked at how energy efficiency, daylighting and overheating were
affected by changes to glazing, frame width, window area and the orientation of
the property.
The guide studies
four types of home, ranging from an average two-bedroomed mid-floor apartment
to a four-bedroomed detached house. It provides solutions according to design
priority and in addition it suggests worst and best case window options for
each home type.
Although final
decisions on window selection for a specific home should be based on more
complex individual calculations, the NHBC Foundation hopes the results of its
research will steer designers quickly to the better or most suitable options
Commenting on the
guide, NHBC Head of Research and Innovation Neil Smith said: "Housing
designers make many technical choices, but few involve as many interactions and
trade-offs as those related to the selection of windows. The challenge for the
designers of today's new homes is to minimise winter space heating demand while
keeping overheating within acceptable limits, and also maximising the amount of
daylight entering the home.
"This guide
reveals the significant and sometimes surprising effects of making changes to
glazing type, width of frame, area of glazing and orientation of the home. It
provides useful aids to help designers easily identify where the most promising
solutions lie for a typical range of home types."
The guide also makes
a number of broad practical observations, including:
- Different home types
did not respond in the same way to changes to window specification: so, for
example, overheating was a significant consideration in window choice for
mid-floor apartments, whereas semi-detached and detached homes were much less
prone overheating;
- Small changes to
‘frame-factor’ have a big impact on performance; and
- Any product
substitutions should be carefully evaluated and monitored during the design and
construction phases: small changes may impact significantly on the energy
efficiency and comfort levels experienced by occupants.
