A conservatory roof can make a noticeable difference to the temperature in the conservatory, depending on its construction. Consequentially, it can either increase or reduce the cost of keeping the area at a comfortable temperature. With modern increased demands on our living space and the recent drive for a usable area to allow working from home, one of the most cost effective ways to gain more all year round space, might be to look at our, too hot in the summer, too cold in the winter conservatory.

A number of years ago, many conservatories were built with a glass or polycarbonate roof. Times and lifestyles have changed as have building standards and techniques. We have learned how we can use changes in building practices to improve the use of our homes, for instance, upgrading a conservatory to a comfortable, warm, year round space, where we can still have a conversation when heavy rain is falling on its roof.

The onset of global warming has heightened everyone’s awareness of carbon emissions and rising fuel costs have made us all look at our energy usage. These factors have prompted governments and industry alike to think smarter about how we build our houses and set us all thinking of ways to improve the energy efficiency of our homes. One of the first areas to be looked at was insulation and this has now led to a situation where rather than just using insulation we are actually thinking about where to make best use of it. How do we maximise its effectiveness?

The construction and insulation of conservatory roofs is a prime example of this drive for maximum efficiency. There are a number of proprietary conservative roofing systems on the market but by varying the way basic roofing materials are used in these roofs, we can achieve either a cold roof or a warm roof, which have differing thermal efficiency. Either way the polycarbonate or glass roof of a conservatory can be replaced with a new solid roof, making it a more comfortable and creating a space that can be use all year round.

A Cold Roof is constructed by laying insulation between the rafters. Although the majority of the ceiling below is well insulated, the rafters which form the roof structure are uninsulated. On the basis that wooden rafters conduct heat much better than insulation, cold air from the outside will conduct through the rafters into the room below. This is known as thermal bridging.

The construction of a Cold Roof, starting from the inside finished ceiling would be;

• Internal ceiling
• Vapour control layer
• Timber joists
• Insulation, laid between the timber joists
• Timber sheeting
• Roofing materials

The insulation in a cold roof is installed at ceiling level, leaving a void between the insulation and the underside of the roof, therefore the void will be at a lower temperature than the room below during colder weather. There is therefore a risk of condensation forming in this void, which can lead to rotting timbers, damp ceiling and ineffective insulation. This means it is important that the void is well ventilated.

The Vapour Control Layer’s main function is to keep warm moist air from inside the building from getting into the roof area and causing dampness.  In a Cold Roof, it is located just above the ceiling and below the insulation. That being the case, it is worth noting that installing down lighters in your ceiling, will mean cutting holes in the Vapour Control Layer, thus limiting its effectiveness.

A Warm Roof is easier to install and offers improved thermal insulation but adds height to a flat roof. As a result of the height difference, you may not be able to install a Warm Roof where balconies or doors lead onto the roof of flat roofs extensions. In these cases, a Cold Roof may need to be considered.

By laying the insulation and Vapour Control Layer on top of the joists, the cold air from outside does not come into contact with the roofing timbers nor does the warm, moist air from inside reach the insulation as the temperature of the joists and the timber sheeting are at the same temperature as the room below. This removes the need to vent the roof.

The construction of a Warm Roof, starting from the inside finished ceiling would be;

• Internal ceiling
• Timber joists
• Timber sheeting
• Vapour control layer
• Insulation
• Timber sheeting (optional)
• Roofing materials

The other advantage of this configuration is that cabling and trunking can be laid in the void between the timber joists and then dropped down the walls rather than being run under the floors and brought up. Also, the installation of down lighters does not compromise the Vapour Control Layer.

A Warm Roof is generally less expensive to install, however, if height is a problem it is possible to cut down on the depth of your joists by the introduction of steel joists. This, unfortunately increases the price substantially.

If you are replacing a polycarbonate or glass roof with a solid one, you are increasing the weight of your roof, particularly if you are using slates or tiles. That being the case it would be wise to seek professional advice as to the ability of the conservatory structure to bear that extra weight

Planning permission is generally only required when the original conservatory is built. However, if the previous height of the conservatory is altered, you may need planning permission, although it’s unlikely. You may, however, need building regulations approval for a tiled roof conservatory. If you have the work carried out by a member of a competent person scheme, they may be able to self-certify compliance with building regulations.

As with all construction or installation related projects, always ensure that you check the credentials of the contractor you are about to use. Make sure they have the relevant experience, qualifications and insurances and check if they are members of a trade organisation or are on a Competent Persons Register.

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