A properly specified warm-deck flat roof will deliver vastly improved energy efficiency over the traditional cold-deck design. A cold deck is constructed as follows: The insulation material is placed immediately above the ceiling between the rafters. It allows insulation to be added without having to replace the waterproofing on the existing roof or raising the roof line. Which makes sense, as this space is otherwise empty, and so it’s a simple, low-impact way to insulate a roof. Materials used for the roof deck should be selected from those listed in BS:6229 2018 It is important to refer to this document for design guidance, but for convenience, the various materials are outlined below: Flat roof design guide. Specifiers have traditionally chosen between two distinct types of flat roof construction: cold and warm. Warm Flat Roofing: This approach uses insulation with no air gap either immediately above or below the roof deck. The position of the insulation dictates which type it is. By ‘majority’, the rule of thumb is that in a domestic house (not flats), approximately a third of the total thermal performance of insulation can be placed below the deck with two thirds above the deck (sometimes this is called a ‘hybrid warm roof’). The insulation is below the deck, but above the plasterboard. I will get you…, Dominic Hayes – Group property Director – Nuffield Health, I am writing on behalf of Thorntons Plc to thank Bradley Mason for the excellent works carried out to our…, Richard Booth – Building and Services Manager – Thorntons PLC, Just a quick note of genuine thanks for a great piece of work, enabling us to achieve our goal! As far as flat roof is concerned, most recommended options are warm deck and cold deck. Now there is a better form of insulation available for your flat roof. The insulation in a cold deck roof is installed at ceiling level, therefore the void is at a colder temperature than the room below during colder weather. North Yorkshire, This is used for refurbishment e.g. A vapour control layer must be used below the insulation. As a result of the height difference, warm roofs cannot be used on balconies and flat roofs extensions with doors leading onto the roof. Well, a cold roof is created by laying insulation between the rafters. Julian and his team provide a great building consultancy service with high quality and thorough reports to quickly to suit…, I’d like to take this opportunity to thank you for the work you have done on this matter, your knowledge…, Thank you for your email of 6 February and for the Dilapidations Assessment. A vapour barrier or vapour control layer is an essential component of any warm roof. This type of construction has the insulation above the roof deck, thus keeping the deck ‘WARM’. Where the existing roof deck is in satisfactory condition and of a suitable material e.g. The cold deck solution. The whole build-up will then be waterproofed with a high performance roof covering, such as GRP Fibreglass, which is certified by the British Board of Agreement to last at least 25 years. The insulation in a warm deck roof is installed immediately below the roof membrane on top of the roof deck, usually with a vapour control layer underneath the insulation. I have forwarded a copy to our…, Thanks Julian super piece of work. In these cases, a cold roof is a preferable alternative to warm roof insulation. It is usually the most acceptable type of construction for domestic possessions and belongings as it avoids the need for aeration of the roof construction. Converting a cold flat roof into a modern warm deck roof can be surprisingly economical. There are two main types of flat roof – cold deck roof and warm deck roofs, do you know the difference? Does a warm deck flat roof need ventilation? Modern polyisocyanurate (PIR) foam rigid flat roof insulation with reflective foil to both sides provides more than double thermal efficiency compared to mineral wool, and unlike the cold roof method the insulation thickness is not limited by the depth of the timber rafters/joists. So i'm looking into a warm deck conversion. What is cold loft insulation? In the case of a flat roof, insulation is usually in the form of either a rigid board above the deck, or a fibrous quilt immediately above the ceiling, depending on the type of roof construction. Ventilation is not needed in a … A cold roof design usually leaves a 50mm gap between the top of the insulation, and the roof deck … The sandwich warm deck roof is the most common type of flat roof. A ‘deck’ is the structural substrate of a flat roof and should be capable of supporting the static and dynamic design loads as well as any loads occurring during construction from machinery and plant. Provided the existing roof is in a good state of repair and has a suitable structure a warm deck overlay can be applied. Really…, Windsor House, Cornwall Road, Harrogate, All Rights Reserved. Inverted warm deck roof The insulation boards in an inverted warm deck are laid over the structural deck and the waterproof covering. Ventilation is required for these roofs. Similar to the pitched roof, a flat roof can be insulated as a cold or a warm deck. This then means that the roof void or deck are at a similar temperature to the room below. It is recommended where possible to use the warm deck method of insulation, where the principal layer of roof insulation is positioned above the structural deck. The roof itself is therefore kept warm. This system is called warm deck insulation and eradicates the condensation and venting issues associated with the cold deck system. This method of insulation can also be used to upgrade the thermal performance of an … Where the insulation is placed above the structural deck (warm deck), and either above or below the waterproofing; there is no need for additional ventilation. Cold Roofs. There are two common forms of construction for flat roofs: • Warm deck (sandwich), or • Cold deck. These types of roof can be more of a challenge to insulate, and generally there are three types of solution. Because this design works by conserving heat, no ventilation is required. The layer of insulation is essentially placed outside of the roof. The insulation is placed below the waterproof covering and is either mechanically fixed or bitumen bonded on to the top of the deck. Hi What roofing material would you be using for your flat roof? The joists are 125mm. Good ventilation (otherwise known as a draught) is essential to allow condensation to escape, particularly where moisture levels are high (such as over bathrooms and kitchens). The Cold Deck is the most common but also the least thermally efficient design of roof insulation. This design dates back many years and flat roof insulation was somewhat of an afterthought with this type of roof. This ensures that your investment in energy efficiency is protected and will continue to pay dividends long in to the future, repaying itself many times over. Cold deck (or cold roof): The insulation is installed below the roof deck. Ventilation is also not required with this type as the design works by conserving heat. Warm deck or cold deck flat roof that is the question. The recognised flat roof build ups for best design practices are: Cold Roof; Warm Roof; Inverted Roof; In the case of a flat roof, insulation is usually either a rigid board above the deck, or a mineral glass/wool quilt immediately above the underdrawn ceiling, depending on the type of roof design and construction. This video will demonstrate how to install a Cure It GRP Waterproofing System in a warm roof build up. This poses a risk of condensation forming within the void or on the underside of the roof slab. Warm deck (or warm roof): The ‘deck’ of the roof is below the insulation. Contrasted with the cold deck roof, this construction has a much lower risk of condensation as the … Inverted roof is very preferable as well. You should have insulation between the joists and underneath and maintain a 50mm air gap between the top of the insulation that is between the joists and the underside of the ply deck. There are three recognised designs of flat roof construction; warm, cold and inverted. The current flat roof design is cold deck. Reinforced concrete. So which is best warm deck or cold deck? Where a cold flat roof does incorporate insulation this is in the form of mineral wool stuffed in between the timber rafters/joists, with a minimum 50mm (2 inch) air gap left clear in between the insulation and the roof deck. refurbishing an existing timber joisted flat roof which has no insulation. Contrasted with the cold deck roof, this construction has a much lower risk of condensation as the void will be of a comparable temperature to the roof. The latter places insulation on top of the roof deck, while the former puts it below (typically between or underneath the roof joists). Deck. Cold loft insulation, or popularly called loft insulation, is a classic roof insulation technique which is simple as well as cheap. The Solution, Warm Deck Insulation Fortunately these days there is a better form of insulation available for your flat roof. The layer of insulation … It will really help in our negotiations with the landlord. Consequently, it is important that the void is well ventilated. A flat roof where the insulation sits below the waterproof membrane and above the structural deck is a warm roof deck. Cold Roof/Deck. A cold deck roof is where the insulation is placed between the joists/rafters or in between the ceiling joists in the case of a pitch roof. The membrane is then attached to the insulation. Cold flat roofs are typically avoided as you’d need to install ventilation, which can prove problematic for many reasons relating to space, labour costs, etc. A cold flat roof is one where the insulation is between or between and below the roof joists. Where insulation depth is restricted by the flat roof construction, it may be necessary to install the roof insulation between and below the joists to create a cold deck structure. A typical warm roof is shown in the sketch below. There are two forms of flat roof construction which can reduce the risk of condensation forming. It is universally recommended that cold deck flat roof construction should be avoided. Call Ashford Building Services today on 01233 626 257. Cold Roof Construction – requires that a suitable ventilated air space exists above the insulation layer, within which the air is constantly mobile, being replenished by fresh incoming air, whilst the air resident within the void space is being expelled via a natural vent action at another point. Deck types for flat roofs. In case of warm roofs they have an insulation above the roof deck, in this way it keeps the deck ‘WARM’. Commonly used flat roofs Warm deck (timber) Warm deck (concrete) Inverted roof (timber) Inverted roof (concrete) Cold deck: 7.1 - Appendix 7.1B Surface treatments acceptable to NHBC: 7.1 - Appendix 7.1C Construction details of flat roofs and balconies: Appendix 7.1-A Commonly used flat roofs. Unfortunately this means a great deal of heat is also lost in the process. This can lead to rotting timbers, damp ceiling and ineffective insulation. Essentially, thermal insulation can either be placed above or below the structural roof deck or waterproofing layer. The membrane is then attached to the insulation. Warm roof insulation ensures the entire roof structure is insulated, meaning a warm deck roof is more energy efficient than a cold roof. Traditionally, flat roofs simply consisted of a structural timber deck with a waterproof covering directly applied to the top of the deck. Flat Roof - Deck. This option avoids the requirement to ventilate the roof. A warm deck roof is much easier to install, offers great thermal performance but adds height to the flat roof. Flat roofs. This design dates back many years and flat roof insulation was somewhat of an afterthought with this type of roof. Flat roof design guide. Copyright © 2021 Bradley-Mason LLP. A cold roof system sees the insulation placed immediately above the ceiling between the joists, with ventilation space above the insulation. Cold Flat Roofing: This is where the insulation is typically packed between the rafters. Ashford Building Services can quickly and economically convert any cold deck flat roof to a warm-deck insulated flat roof, particularly where problems have been tackled sooner rather than later. Furthermore, an Inverted roof is a different type of warm deck roof, where the insulation is installed above the membrane and so no vapour control is needed. In flat roof construction thermal insulation can be placed above and below the structural roof deck or waterproofing layer. This should ideally be in the form of ‘soffit vents’ to the underside of the fascia boards, but as many flat roofs were built without soffits, it is often in the form of unsightly ‘mushroom vents’ on top of the roof, or soffit vents incorrectly fitted in to the fascia boards. In the case of a flat roof the roof deck and waterproof membrane are supported on joists, the internal ceiling is attached to the underside of the joists and should have a vapour barrier to stop condensation penetrating the internal decor. This is usually the most satisfactory construction for domestic properties as it avoids the need for ventilation of the roof structure. This system is called warm deck insulation and eradicates the condensation and venting issues associated with the cold deck system. Traditional cold deck flat roof Traditionally, flat roofs simply consisted of a structural timber deck with a waterproof covering directly applied to the top of the deck. Insulating a timber deck flat roof can be done using warm deck construction method or cold roof construction method. Less thermally efficient than a warm roof construction, cold roof construction remains the most common form of construction for existing flat roofs. This was the traditional way of flat roof construction and as insulation has increased over the years, the warm deck roof is now the commonly used method of construction. Good external ventilation is also essential to minimize the risk of condensation in a cold roof. There isn't enough space in the void for more insulation and an air gap. A warm roof deck is the most common and most preferred type of flat roof build up in the UK. Section 25 Notices – Lease Renewal under the Landlord & Tenant Act 1954. For most domestic purposes a warm deck flat roof is superior to a cold deck. The insulation in a warm deck roof is installed immediately below the roof membrane on top of the roof deck, usually with a vapour control layer underneath the insulation. Cold deck roof construction is still a current method used (unless this has changed in the last couple of weeks). plywood, the insulation is fixed directly on top, often with the existing felt acting as the vapour barrier. Warm Roof By moving the insulation to the outside of the structure, the roof deck is effectively brought inside, which results in a ‘warm deck’ (hence the name), this removes the the possibility of condensation forming on the underside of the deck and eliminates damp. This gap is necessary to allow air-flow, so that warm, moist air, is allowed to escape rather than coming in to contact with the ‘cold deck’ and condensing. 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