ISOVER: White House Industrial Estate, Runcorn, Cheshire, WA7 3DP. Then rafters are a good choice, since they don’t have to be ordered and built ahead of time. In this guide, we will define roof trusses and rafters and explain the pros and cons of each for comparison. There’s a lot to like. They are built in a controlled environment. Excellent Strength and Span: The webbing effect of the truss members creates outstanding structural strength, even though smaller lumber is used. There is an enormous amount of unused space in there! With a warm roof the usual process is to split the insulation into two layers. 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 Getting to Know… Kingspan Kooltherm K7 Pitched Roof Board. Saint-Gobain Construction Products UK Limited trading as Celotex, Registered in England. While trusses and rafters can handle similar loads, there are clear distinctions in essential areas that will help you choose which is right for your building project. Price: When the cost of a prefabricated truss package is compared to the material and labor costs to build rafters on site, the cost of trusses is 30% to 50% less. The joists might then be covered with OSB or plywood to form an attic floor for storage. The are similar to trusses in this regard. Arguably the most popular pitched roof solution, installing insulation between and under the rafters uses the depth of the structural timbers to best effect. Ceiling Design Limitations: The structural webbing of trusses limits what you can do with the space beneath and between them. Don’t need it for living space? This means pipes and water tanks in the loft space could be more likely to … Fasten insulation boards to the roof sheathing per the following options: a. It does not constitute advice and should not be relied upon. with rgards to fitting kinnspan between irregular rafters, the best technique is to cut slightly over size the hold the insulation up to the rafters and give it a good sharp knock, then cut along the imprint made by the rafters … If you’re building in the spring, the boom or crane company might say, “We can’t get our equipment onto the worksite until the muddy ground dries up.” That could cause unexpected delays not common to building with rafters. The unvented attic is indirectly conditioned space since heat and moisture transfer occurs through the top floor ceiling, particularly if the ceiling is not airtight. T: 01473 822093. Rafter-level insulation combined with ceiling insulation can be used together where an existing attic space is converted. The major functional difference between the two is that trusses are built mostly with 2x4s in place of the wider dimensional boards. Building with them is known as stick framing. You can use a utility knife to cut using the same cut and snap process you use with drywall. Celotex polyisocyanurate (PIR) foam insulation boards are easy to cut and handle. Permeable insulation … Once up at roof level, the between-rafter boards can be cut accurately to fit the rafter spacings. The flexible nature of GMW means that the roll or batts can be accurately-cut and friction-fitted between the rafters – thereby minimising air gaps and maximising thermal performance. This slows the project, and the framing is susceptible to weather for much longer. Zero Lead Time: Going to work on a project “spur of the moment”? Common rafter depths range from 100mm to 200mm. Batts between rafters in would require adding ventilation between the insulation & roof deck. When it comes to pitched roofs, however, adding a thick layer of insulation to the rafters can result in a depth of roof construction that may not suit every site, meaning over-rafter insulation (sarking) only is not a viable option. Weight and Size: Assembled trusses are big and heavy. There’s more on the pros and cons below, but first let’s define the terms: Rafters are the traditional means of framing a roof. We’ve seen that too. This limits the maximum thickness of the insulation between the rafters to between 50mm and 175mm. Accuracy: There are fewer mistakes made in the fabrication of trusses. If 180mm is to be installed then 100mm board might be introduced between the rafters (there has to be a minimum 25mm air gap between the insulation and the underside of the tiles or slates) with an 80mm board running across the rafters. Whether you need to insulate your roof rafters will depend on what you intend to do in the space directly beneath the rafters. The most commonly used form of roof insulation in sloping roofs is insulation between rafters. They’re more economical to build and offer the same or greater roof strength. Saint-Gobain Isover UK Limited, Registered in England. Building is labor-intensive. Cuts are automated for tremendous precision. Registered Offices: Saint-Gobain House, East Leake, Loughborough, Leicestershire, LE12 6JU. This means insulating between or below the sloping beams that form the construction and support a sloping roof. Insulating between rafters will do no good, because the attic should be ventilated, and the rafter insulation would be between two unheated spaces. Tel +44 (0) 800 032 2555. Rafters are a better choice for specialty projects. Cost: When materials and the much-higher labor rate is factored in, rafters are the clear loser in the cost battle. Here, the thermal insulation is precisely installed between the rafters. ISOVER glass mineral wool (GMW) is another option for the between-rafter insulation either as a roll or batt. This means a couple things. The material can be brought in on a pickup truck or boat, if necessary. Go with insulation between and over or between and under the rafters. 3. The rafters are … Being … It is common to read that “rafters are the way they used to frame roofs. Our insulation solutions for warm roofs maximise both space and thermal efficiency, whilst also contributing to acoustic performance. We will also outline the best uses of each, so you can decide whether rafters or trusses are the right choice for your building project. For this method of pitched roof insulation, we recommend using Mannok Therm Roof / MR Insulation boards between the rafters and Mannok Therm Laminate-Kraft / MLK Insulation boards below the rafters… Company Number 734396. One of the most cost-effective insulated ceilings is to install IsoBoard as a roof-liner over trusses, beams and rafters. Ridge Board… You can also add rigid foam insulation under the rafters, which adds R-value and eliminates thermal bridging through wood rafters. Insulating the rafter space will give you a warm loft. Once up at roof level, the between-rafter boards can be cut accurately to fit the rafter spacings. See costs in your area A vent baffle should be installed between the insulation and the roof decking to maintain the ventilation channel. Pricey, yes, but at least possible compared with getting trusses to that sort of remote building site. As the council are paying75% of the cost i would make them my first point of call. In finished space, insulation is placed between the rafter boards and drywall or other material is fastened to the face of the boards. It typically has 3 variations: bare foam board, one sided sheathing board or double sided which … (“Saint-Gobain Insulation UK”, “Celotex”, and “ISOVER”) The key practical difference is that trusses are built in a factory (pre-fab) under ideal conditions. Tel +44 (0) 1473 822093. © Copyright 2021 Saint-Gobain Insulation UK (comprised of Celotex and Saint-Gobain ISOVER UK Limited. Convenience Polyurethane or polystyrene spray foams can provide thorough coverage to roof rafters … It can be advantageous to combine more than one of these approaches – for example, by insulating between and below rafters. Insulating between the joists of your loft will keep your house warmer, but make the roof space above colder. Being lightweight, they do not impose significant additional loads on existing structures. If inclement weather rolls in, expect delays as the entire structure gets tarped to wait out the rain. The building detail is for illustrative purposes only. Your truss package will come with detailed installation instructions for spacing and fastening. Pitched roofs can be insulated between, below or above the rafters. If trusses were perfect, this discussion would be useless. Uneven or sloppy application, however, can make the insulation ineffective, and unsealed open-cell insulation can absorb moisture, causing the roof to rot or leak. You want to maximize living space within the home’s structure. Kingspan Kooltherm K7 Pitched Roof Board is a premium performance rafter-level insulation for ventilated or unventilated pitched roofs. On the same home, rafters might take a week, depending on the size of the crew. Good luck getting the trusses to your property! Use them Anywhere: Since rafters are stick built on the job site, they’re ideal for hard-to-reach building locations. Insulating Rafters When installing rigid foam insulation between roof rafters it is standard to use foam boards that are not as thick as the depth of the rafter space. At worst, heavy rains during construction can lead to damage to the home’s structure that requires an insurance claim. Their sheer weight makes them more difficult to work with, especially when they span 40 feet and beyond. To compensate for using materials that aren’t as strong, more material is used. This generally would not be a … Use a chalk line or T-square to mark where it needs to be cut. The benefits of insulating a building around the outside, protecting the structure and effectively creating a ‘tea cosy’ effect, are well publicised. Specifications are loaded into software, and truss components are digitally measured and cut. Rigid foam board is just above the roof deck, or an exterior insulation option. Time and Weather Risks: Truss installation takes about a day on most 2,500 square foot homes. As the load goes up for snow in northern climates or for heavy roofing material like tile, the span length decreases. We’ve seen rafter material transported by helicopter. Forget about a finished attic. The board, in addition to providing high levels of thermal insulation, … Where the insulation does not fill the total rafter depth, the low-emissivity foil facings can gain additional thermal benefit from the air spaces they face into. Pace: The pace of building slows noticeably once the walls are up and work shifts to hand-building each and every rafter. Put the board between the rafters. Consider opening it to the lower floor to create a truly dramatic vaulted ceiling. Skill Required: Factoring angles on stick-built rafters is complex. Secondly, rafters can have important advantages over trusses in certain building projects; If you’re planning an out-of-the-ordinary, custom roof design or want to make use of the attic space, then rafters might be more appropriate. Here are a few cons for trusses. Its versatility is the key to its … Ideally, an additional insulation layer of ISOLAIR or PAVATHERM-PLUS … DIY Friendly: Truss installation is much easier than building rafters one at a time. Roofing Calculator - Estimate Roof Costs - RoofingCalc.com. You might need to rent a boom or crane to get them to the roof. Internal restrictions, like maintaining sufficient head height, can mean that fixing the insulation between and under the rafters is not an option either. Advantage truss, it’s the best way to get your roof done fast, easy, and correctly. Here is how we cut and fit our PIR insulation to insulate the walls and roof of the house. I also hand-built all 11 trusses in about three hours – so I think I can build one anywhere I can build the rest of the house. This diagram shows the major components of a traditional rafter, though slightly different styles can be built. However trusses don’t give you the opportunity for creativity in home design that rafters allow. 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