Suppliers - ‘Help to Control the Conservatory
** An article all about making
your conservatory more comfortable and useable all
year round – sponsored
by: Insupolycarbonate™ Roofing **
Conservatory Companies: Are you looking for products that can be
added to their range for competitive advantage, or
to meet the competition, and for information on how
to improving the design of their conservatories.
Question One: Recently several conservatory companies
in my area have changed over completely to 25mm, 32mm,
or 35mm Polycarbonate roofing, or to Glass roofing
incorporating solar heat reflectors. They are promoting
these new products as an integrated solution that both
avoids the need to subsequently retrofit shading to
control high summer temperatures, which also allows
economic heating of the conservatories in winter. What
are the advantages and disadvantages of these types
of roofs and how do they compare?
Although the use of these types of roof is not yet
mandatory, as the forthcoming Building regulations
for conservatories have not yet been introduced, many
conservatory companies have upgraded their designs
to enable customers to benefit from a significantly
higher standard of winter insulation, and protection
from excessive summer temperatures that these new roof
The insulation standard specified
by Document ‘L’ the
forthcoming Building regulation is for a ‘U’ value
or heat loss factor of 2.0, shortly to be reduced to
1.8. It is the author’s view that this is still
to high, especially for conservatories shaded from
the winter sun, on exposed sites, and further north
in the country. A more appropriate value would be generally
1.4 to 1.6.
There is little to choose between the insulation values
of the various thickness of polycarbonate roof glazing.
A 25mm five wall grade with solar heat reflectors will
bring the U or heat loss factor down to as low as 1.4
which is half that of the previous standard triple
wall 16mm polycarbonate. Many conservatory companies
market the thicker sizes on the basis that a thicker
sheet is a better standard, which is not necessarily
Modern double glazing comes with
a low emitting surface, similar to ‘K’ Glass, on the inner pane
of the double glazing unit which faces into the cavity,
this significantly reduces radiation heat loss between
the inner room side, and outer, external glazing. The
cavity between the two sheets can be either air or
argon filled. Argon has a lower thermal conductivity
than Air and a higher winter insulation performance.
Typical Argon filled units have ‘U’ values,
or heat loss factors, of 1.2 to 1.4, Air filled cavities
are higher at 1.8. Either of these can be supplied
with solar heat reflecting properties, which should
exclude a minimum of 70% of the solar heat to achieve
acceptable summer temperatures.
Polycarbonate roofs incorporating solar heat reflectors
to exclude excess summer heat have noticeably better
winter insulation values than Polycarbonate alone.
As a result they are increasingly in demand since customers
wish to use their conservatories as part of the house
in both summer and winter.
The new generation of performance glazing offers conservatory
companies considerable commercial advantages, as customers
readily recognise the advantages of summer and winter
comfort, and lower fuel bills, and are willing to pay
for these benefits. Conservatory companies can therefore
sell these products at premium prices and benefit from
Question Two: What are the advantages and disadvantages
of Tinted glass and Opal and Tinted polycarbonate roofs.
Tinted glass is often specified in the mistaken belief
that it will have some benefit in reducing high summer
temperatures, and cutting glare. This is not so as
tinted glasses are only designed for side windows,
not roof glazing. They do not, therefore, have the
performance needed for this far more demanding environment
where the sun is on the roof all day long, and one
is surrounded by brightness from the glazing, and reflections
from light coloured surfaces.
It is necessary to exclude in
excess of 70% of the sun’s heat entering through the roof to control
temperatures, the specification for tinted glasses
falls far short of this. Also there is very little
glare control with a tinted glass in the roof because
of the sheer area of glazing which easily overload
the eye with light. The problem is most acute for the
Polycarbonate roofs come in a
variety of finishes for example: Tinted Bronze and
other colours and Opal.
The tints absorb the sun’s heat and the roof
becomes warm. They therefore do little to control temperatures.
The only effective way to cut high temperatures is
to reflect the sun’s heat out before it enters
the conservatory. This can be achieved by incorporate
solar heat reflectors within the outer cavity of the
polycarbonate roofing which exclude up to 80% of the
sun’s heat before it enters the conservatory
to reduce temperatures to comfortable levels.
Tinted polycarbonate is effective at controlling glare
but at the expense of a significant reducing in light
levels. This can cause complaints of inadequate light
especially in adjacent rooms, during winter and on
It is important to ensure that the tinted polycarbonate
is sourced from a reputable supplier as tints can bleach
out during the life of the roof.
Opal polycarbonate is often specified by conservatory
companies because it hides condensation that may be
present within the roof cavity, and it masks the appearance
of debris, algae, marks and bird droppings on the outside
of the roof glazing.
Question Three: What level of ventilation should be
incorporated into the conservatory design and how is
this best achieved?
Most conservatories have inadequate levels of ventilation
because of over-riding concern to keep costs to a minimum,
and a poor understanding of both conservatory design
considerations, and the efficiency of various types
of windows and roof vents.
It is important that conservatories are fitted with
a minimum area of window openings, which must be positioned
correctly to allow for cross flow ventilation. The
efficiency of the window types is important because
the free flow of air through different types of windows
can vary dramatically.
Roof vents provide higher levels of exit ventilation
but they need to be fitted with adequate provision
for air entry.
Regrettably many conservatory salesmen will compromise
ventilation when under perceived or actual pressure
to reduce the price of the conservatory. They do this
by eliminating some of the opening windows, which are
more expensive, to reduce the price. The result is
a technically inferior conservatory of lower quality
and environmental problems for the new and subsequent
Question Four: We receive complaints from customers
who have bought lean-too conservatories that there
is condensation within the polycarbonate flutes, towards
the lower end of some of the roof panels. What is the
cause of this and how can we ensure that future conservatories
of this type do not suffer from this problem.
Condensation within the flutes of the polycarbonate
is not unusual and it is not a cause for concern. It
occurs for several reasons including:
1. Inadequate pitch of the roof,
2. End cappings fitted short which allow water to drain
directly into the end capping channel,
3. The leading edge of the end cappings has been left
unsealed which allow water to drain beneath into the
flutes of the roof.
4. Poor quality breather tape.
It is commonly assumed that polycarbonate roofing
is impervious, this is not so. On shallow pitch roofs,
where water drains more slowly, diffusion of moisture
vapour from the outside into the inner structure of
the polycarbonate can lead to the appearance of condensation.
It is important that correct sealing procedure is
followed when fitting the end cappings, especially
if the roof pitch is below the recommended angle. For
example if the roof has to fit below a gutter on a
bungalow. If problems still occur after all recommendations
have been followed, then additional means of drainage
and air-circulation have to be employed. Fortunately
these are simple and straightforward.
It is essential that these additional measures are
employed in conservatories that form part of a swimming
pool, or in polycarbonate roofed swimming pools. Otherwise
diffusion of moisture from warm high humidity air below
the roof into the roof cavities will cause a build
up of condensation.
Question Five: We do not recommend
the installation of roof vents into our customers’ conservatories
as we are concerned about call-backs if leaks occur.
However we recognise the need for improved levels of
ventilation to control high summer temperatures, and
feel we ought to be able to offer this option with
confidence. Can you recommend any specific designs
that are free from leak problems?
There are two crucial design considerations.
1. It is important that the roof vent bridges, and
locks solidly between, the roof support/glazing bars
in the same way as the roof glazing panels. A glazing
panels is therefore made incorporating the roof vent,
this comprises of three parts : a top glazing panel,
a middle part - the roof vent, and a lower glazing
panel. The top panel is glazed into a rebate on the
upper side of the roof-vent, the lower glazing panel
is glazed into a rebate on the lower side of the roof-vent.
This design ensures that leak problem due to flexing
of the glazing panel and expansion and contraction
2. There should always be an adequate up-stand around
the aperture of the vent to prevent it being flooded
by a heavy down poor, and a well fitting deeply rebated
top cover that locks down on top of the up-stand. Careful
adjustment may be necessary to ensure that when closed
the up-stand and rebated top cover fits accurately
and locks down tight onto the upper seal.
Care should be taken if the roof-light is assembled
on site to ensure that the sealer used to assemble
the panels does not block any of the internal drainage
Everyone (trade and general public)
is welcome to request the very informative “Guide
to Controlling the Conservatory Environment”
Editorial provided by and sponsored by: Insupolycarbonate™ Roofing
the INSU websites at: http://www.insu.co.uk and http://www.insupolycarbonate.com