(“Saint-Gobain Insulation UK”, “Celotex”, and “ISOVER”) Saint-Gobain Insulation UK manufacture and supply glass mineral wool slabs and rolls along with rigid Polyisocyanurate (PIR) boards that can be considered suitable for a wide range of applications across flat roofs whether you’re looking to insulate at joist level or above the roof deck in your flat roof construction. The sheets of plywood are fixed to the flat roof joists to make a flat base, hence the name flat roof. Cold Flat Roof: Many properties use this option, as there are no additional costs for scaffolding or organising how to gain safe access to the roof exterior. ISOVER Acoustic Partition Roll (APR 1200), flexible glass mineral wool (GMW) roll or slab from ISOVER, insulationuk.marketingteam@saint-gobain.com, Spacesaver: Width 1160mm, Length 5200-12180mm | Spacesaver Ready-Cut: Width 3x386 or 2x580mm, Length 5200-12180mm | Spacesaver Lite: Width 1160mm, Length: 3500-7000mm, Widths 2x570mm, 3x400mm (140mm only), Length 4000-5300mm. Register to gain access to our comprehensive technical library which contains helpful specification tools, including BIM objects and much, much more... E: insulationuk.marketingteam@saint-gobain.com A cold deck flat roof will typically require insulation to be installed between the roof joists to … This means there is a vapour control layer in the ceiling and cross ventilation at the eaves or the top of the walls. In the warm flat roof construction, there is insulation packed into every possible space where air can flow. No ventilation is required for these types of roofs. The depth of insulation is dependent on the U-values required and the depth of the roof joists, always allowing for a minimum 50mm air gap. Tel +44 (0) 800 032 2555. This is used for refurbishment e.g. In the Mannok insulation range, there are a number of suitable insulation products for use in this particular type of roof construction. Flat roof design guide. Reset calc. Rigid PIR insulation boards, such as Mannok Therm Roof / MR boards, are generally the preferred roof insulation materials for flat roofs for a number of reasons.They are lightweight, easy to fit and come in a range of thicknesses. Timber post . Flat roofs have often been built with the insulation all on top of the vapor closed drainage plane - as this avoids dew point condensation issues inboard of the roofing. refurbishing an existing timber joisted flat roof which has no insulation. Pipes, water tank and loft hatch Insulating between the joists of your loft will keep your house warmer, but make the roof space above colder. A cold roof is the most common type there is, where the insulation is laid on top of the ceiling between the joists. We’ve watched your video on YouTube and wonder if you could give us some advice please…. Although cold roof systems were used extensively in the past, they are now considered out of date and are highly inadvisable. Flat roof. Don't have an account? The major difference between the warm flat roof and the cold flat roof has to do with the air flow between the roofing timbers (known as “joists”) that help to hold up the roof. To calculate U-Values specific to your roof construction, use our free U-Value calculator. Ventilation is required for these roofs. Mannok Therm Laminate-Kraft / MLK insulation boards, Mannok Therm Roof / MR PIR insulation boards, Mannok Therm Laminate-Kraft / MLK PIR insulation boards, Insulating solid ground floors below ground bearing slab, Insulating solid ground floors with a timber floating floor, Insulating solid ground floors above ground bearing slab, Insulating suspended beam and block floors, Insulating suspended timber ground floors between timber joists, Insulating suspended timber floors other than ground floor between timber joists, Insulating a pitched roof above the rafters: warm roof insulation, Insulating a pitched roof above and between the rafters: warm roof insulation, Insulating a pitched roof between and below rafters: cold roof insulation, Insulating a loft or attic wall in pitched roof space, Insulating a flat roof with concrete deck, Insulating a flat roof with timber deck insulated above the joists: warm deck insulation, Insulating masonry cavity walls with partial fill insulation, Insulating masonry cavity walls with full fill insulation, Insulating masonry cavity walls with internal dry lining, Insulating solid walls with internal dry lining – insulation boards fixed to battens, Insulating solid walls with internal dry lining – insulation boards fixed by battens, Insulating solid walls with internal dry lining – insulation boards fixed by dabs, Insulating timber frame walls with weatherboards. TLX Silver can be used to reduce the thickness of additional insulation required between the joists to help ensure a ventilated gap is maintained between the insulation and the deck. Company Number 734396. Cold Deck/Roof 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 insulation material is placed between the supporting joists, leaving a gap of 50-60mm between the roof and insulation. A cold flat roof is where the insulation is placed between the joists under the flat roof, so that the roof and the roof timbers are cold. cold deck: this is where the insulation is placed between the joists/rafters or in between the ceiling joists in the case of a pitch roof. Install Mannok Therm Laminate-Kraft / MLK insulation boards below the joists using suitable mechanical fixings. By far and away the most common type of roof is the cold roof and as this does not need specialist advice to fit this is where we will focus. roof insulation between joist. One of the most essential considerations in a cold deck flat roof construction is the requirement for adequate ventilation in the form of a ventilated cavity of at least 50mm between the underside of the timber deck and the roof insulation below. Saint-Gobain Construction Products UK Limited trading as Celotex, Registered in England. Ventilation openings must be left at each end of every air space. Saint-Gobain Isover UK Limited, Registered in England. There are three recognised designs of flat roof construction; warm, cold and inverted. Register for an account, Flat roof: timber deck insulated between and below joists: cold deck insulation. A cold flat roof is one where the insulation is between or between and below the roof joists. The waterproof layer is above the insulation and a vapour control layer is placed below the insulation. Cold flat roof insulation Lots of traditional flat roofs are of the ‘cold roof’ construction type. On new build or replacement pitched roofs, the ideal build up would be insulation fitted over and then between the rafters — giving a big boost for airtightness (Image credit: Kingspan) With a flat roof, this issue does not arise, but the U value constraint and the amount of insulation needed is just the same. Using Mannok Therm Laminate-Kraft / MLK insulation to insulate below the roof joists will also help achieve optimum thermal performance and it also eliminates the need to install an additional vapour control layer and a separate plasterboard layer. The openings must be equivalent in area to a continuous opening of 25mm along each side. The external wall insulation needs to be extended up to the underside of the roof insulation to prevent cold bridging. To increase the thickness of your roof insulation layer, you can: Lay mineral wool between the joists and then fit rigid insulation boards across the joists, with floorboards on top. There are two basic categories of roof design: A warm roof has the insulation above the structural deck, which is thus kept warm. To form a vapour control layer, seal the joists between the boards. Insulation is placed over and between the wooden joists, above the ceiling of your home's top floor. 10mm wider then necessary) to ensure a friction fit when installed between the joists. Flat roof insulation always requires professional insulation and damp roofs require professional assessment before work can be carried out. Rafters . Example 3 – A Cold Roof With Extra Insulation Above the Ceiling. However in many situations the insulation may need to be primarily or entirely below the flat roof membrane and between the roof joists - if so, what are the best options? U-value results above based upon pitched roof construction shown: 12.5mm plasterboard; AVCL; Mannok Therm Roof / MR; roof joists; Mannok Therm Roof / MR between joists @ 400mm centres; timber deck; waterproofing layer (built-up felt shown). This wool is packed into the joists and rafters a clear gap of 5cm is left between the insulation and the timber board to allow condensation to escape this is to prevent the condensation making contact with the boarding or deck…. Either a rigid PIR board from Celotex can be cut to an exact fit and installed between the joists, or a more flexible glass mineral wool (GMW) roll or slab from ISOVER can be cut slightly oversize (i.e. Calculations performed to BS EN ISO 6946, taking account of repeating thermal bridges. The below U-Value table shows the thickness of insulation to use to achieve a range of U-Values using Mannok Therm Roof / MR and Mannok Therm Laminate-Kraft / MLK PIR insulation boards. The rule of thumb for foil faced boards (like Thermapitch TP10 or Kooltherm K7) in this scenario is that you can have no more insulation under the joists than you have between the joists. The underside of the rafters in this case will need to be finished with a suitable vapour control layer (VCL) and plasterboard to provide a suitable internal finish to the roof. Registered Offices: Saint-Gobain House, East Leake, Loughborough, Leicestershire, LE12 6JU. Cold Deck Roof With this type of roof the insulation is placed between the flat roof joists at ceiling level. Cold Deck – this is where the insulation is placed between the joists/rafters or in between the ceiling joists in the case of a pitch roof. A cold flat roof does include insulation typically by way of Kingspan or Celotex insulation material inserted between joists. © Copyright 2021 Saint-Gobain Insulation UK (comprised of Celotex and Saint-Gobain ISOVER UK Limited. 100mm Therm between Studs. It already has foil-backed insulation in the roof but only 35mm and we would like to increase this – without taking the roof off, as it’s simply too expensive. Ventilation is required for these roofs. Lay 12mm of plywood or OSB board across the timber joists as a base for the flat roof build-up; Install a vapour control layer to reduce the risk of condensation and moisture compromising the flat roof structure It will stop the heat escaping from the living area of … If you’re seeking a reduction in energy usage (and your energy bills), warm flat roof insulation will work best for you. Warm Roof 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. This method of insulation can also be used to upgrade the thermal performance of an existing roof without affecting the waterproofing system. ISOVER: White House Industrial Estate, Runcorn, Cheshire, WA7 3DP. Mannok Flat Roof insulation is foil faced on both sides and should be used to insulate the flat roof between the joists to achieve optimal thermal performance. The simplest and cheapest roof insulation is the classic cold loft option. We recommend a combination of Mannok Therm Roof / MR boards and Mannok Therm Laminate-Kraft / MLK insulation boards. The panels are laid with the longer edges across the flat roof joists and staggered to offer a more stable surface. 3. The traditional cold deck flat roof system is to install the insulation between and under the joists, with ventilation below the timber deck. 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. Using Mannok Therm Laminate-Kraft / MLK insulation to insulate below the roof joists will also help achieve optimum thermal performance and it also eliminates the need to install an additional vapour control layer and a separate plasterboard layer. 2. This is often just called loft insulation. 1. For this reason i would prefer to have insulation between the joists as with a cold flat roof construction. The insulation is below the deck, but above the plasterboard. Stud wall . Therefore, the cold roof ventilation needs to be provided to create airflow to the front and rear of the roof to prevent condensation. Cold deck or cold roof is where the insulation is below the roof deck (and the associated joists). This will enable the airflow to circulate freely. Insulating above and between the roof joists is probably the preferred solution, and this method is often used in new-build and in retro-fit. The majority of domestic cold flat roofs use insulation ‘between and under’ the joists. FLAT ROOF DORMER. As a consequence: Alternatively, battens can be secured to the underside of the joists and GMW fitted between these in much the same way as between the main roof joists. Welcome to MANNOK, the new name for Quinn, Click here to find out more about our new brand, Vented airspace between Mannok insulation and timber deck. It does not constitute advice and should not be relied upon. Insulating a flat roof is relatively simple in terms of what materials you need, and the steps taken to complete the job. Flat roof insulation projects are less complicated than those of pitched roofs. This ventilation is necessary to prevent condensation from forming below the roof deck, which can cause rotting to the timber deck and compromise its load bearing capacity. Cold roof – a very bad idea! A cold deck flat roof will typically require insulation to be installed between the roof joists to comply with Building Regulation requirements. 2. Please view our Cookie Policy page for further information on cookies used by Mannok. Set the boards onto a wide (30mm) bead of vapour resistant sealant applied to the under surface of all the joints and cross noggins or alternatively a separate AVCL can be installed. This may help with condensation, but causes such a loss of heat that it has been banned in Scotland. Good question, theoretically when building a warm roof the Vaper control layer goes on the warm side of the insulation. Purlin . Calculations to BS5268-2:2002. 1. Both the vapour control layer and plasterboard are in-built in the Mannok Therm Laminate-Kraft / MLK board, making it much easier and more efficient to install the insulated structure. Tel +44 (0) 1473 822093. The building detail is for illustrative purposes only. Fit the cut Mannok Therm Roof / MR insulation boards tightly between the joists. Flat Roof. Measure the space between the joists where the insulation will be placed accurately and cut the Mannok Therm Roof / MR insulation boards marginally wider than the space to ensure a friction fit upon installation. Depending on the building use insulation could be required to construct a ‘warm roof’ build-up. In fact, insulation from the inside will inevitably lead to the formation of condensation caused by the humidity present inside the building. Application - Flat Roof Applications Flat Roof Insulation including above, above + between, between + below, and below joists. We use cookies to ensure that we give you the best experience on our website. Flat Roof Joist Calculator. Thermal bridging also needs to be carefully addressed when installing insulation in a cold deck flat roof in order to achieve the required U-Values and improve the thermal efficiency of the structure. If you put insulation under the decking and between the joists you lower the temperature of the decking and lower the due point thus bringing it closer to the danger point of being in the building. For help and advice on any of our products and how they might fit your needs please contact our Technical by Mannok team. Different Types of Insulation for a Cold Roof. A cold roof has the insulation placed below the structural deck, which thus remains cold. As you can see from the image below, this design is still a cold roof, but there’s now 50mm of ventilation, a water vapour barrier and extra insulation between the ceiling and the roof. A gap of 50mm must be left between the upper surface of the insulation layer and the timber deck above to form the ventilation cavity. 100mm x50mm studs @ 400mm centres. Unless the joists are exceptionally deep there is also likely to be a requirement to install insulation to the underside of the joists, as the upper 50mm of joist space is usually required to be left clear for ventilation purposes. Last year we bought a barn that was converted in the 1980’s. CELOTEX: Lady Lane Industrial Estate, Hadleigh, Ipswich, Suffolk, IP7 6BA. You could even buy insulation and floor boards that are already bonded together, which makes the job much faster and easier. Flat roof joists . By continuing to browse the site, we will assume that you are happy for your web browser to receive all cookies from our website. There are two approaches to installing flat roof insulation; warm flat roofing works by placing the insulation material on top of the roof, while cold flat roofing involves placing insulation between the joists. Warm Deck – The type of insulation for this is usually of a rigid type and the thickness will vary depending on … More importantly, they have excellent thermal properties and compressive strength, which makes them ideal for flat roof insulation. Some forms of roof decking may also have insulation bonded to them. T: 01473 822093. Mannok Flat Roof insulation is foil faced on both sides and should be used to insulate the flat roof between the joists to achieve optimal thermal performance. Company Number 10442670. As for insulating below the joists, an insulating laminate (insulation bonded to plasterboard) such as Celotex PL4000 or a separate rigid PIR insulation board finished with a separate sheet of plasterboard can be securely fixed to the joists to provide an internal finish to the roof. 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