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Conservatory Suppliers - ‘Help to Control the Conservatory Environment’

** An article all about making your conservatory more comfortable and useable all year round – sponsored by: Insupolycarbonate™ Roofing **

Controlling the Conservatory EnvironmentAttention 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 materials provide.

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 the case.

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 improved margins.

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 over 50’s.

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 dull days.

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 owners.

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 are eradicated.

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 channels.

Everyone (trade and general public) is welcome to request the very informative “Guide to Controlling the Conservatory Environment”

This Editorial provided by and sponsored by: Insupolycarbonate™ Roofing

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