PIR insulation boards help building owners reap the benefits of green roofs, says EcoTherm® Marketing Manager Dale Kaszycki.
Green roofs can bring many environmental benefits, but their contribution to energy efficiency is officially disallowed because they might be removed. Teamed up with polyisocyanurate (PIR) insulation boards to achieve compliance with Building Regulations, however, green roofs take thermal efficiency and potential energy savings to new highs.
During the past 25 years the construction industry across the UK and Europe has come to realise the considerable benefits of rigid polyisocyanurate – essentially the highest insulation values from the minimum thickness of material. Thermal standards have risen dramatically and PIR has accommodated the changes with minimal effect on application techniques. The current focus on green roofs creates a new opportunity for PIR thermal insulation boards, which are suitable for flat and pitched roofs as well as floors and walls. PIR thermal insulation boards have become increasingly popular on residential, commercial and industrial projects as they offer the ideal combination of exceptional insulating properties, high strength and light weight. They are easy to handle and install and they allow light supporting structures.
Of course, the blanket of plants, roots and substrate making up a typical green roof is a surprisingly good form of insulation on its own. It also acts as a giant sponge in wet weather, reducing rainwater run-off and pressure on local drains – and potentially cutting the risk of localised flooding. When the summer sun stimulates evaporation, a green roof is a valuable natural source of cooling. Green roofs bring biodiversity back into heavily built-up urban areas, attracting birds and insects, while the plants in the roof absorb some of the excess CO2. Finally, a green roof provides generous protection for the essential waterproof membrane beneath it – extending its useful life by a two to three times and significantly reducing re-roofing costs through the life of the building.
Despite all this, green roof coverings don’t count in U-value calculations for roof constructions because, in terms of European standards, the planted green element is not considered permanent. Accepted U-values are based only on the combined ‘muscle’ of the supporting elements – typically a metal roof deck, an insulation material such as PIR and a waterproof membrane, with the insulation clearly the major performance contributor.
In reality, if the required U-values are achieved with conventional materials, the addition of a green layer should make the roof super-efficient, keeping greater proportions of winter heat inside and summer heat outside. This means less requirement for energy hungry heating systems in winter or air conditioning in summer. It also facilitates more efficient performance of heating and cooling systems.
All these factors add up to a strong case for green roofs in planning terms. In short, a solution which can push up an EcoHomes rating by almost 7%, provides a sustainable design technique for increased energy efficiency in buildings and positively contributes to sustainability and local biodiversity makes a pretty compelling case to lay before planning authorities.
Stepping away from green roofs for a moment, it is a fact that good insulation is recognised as a key factor in helping to achieve required standards of energy efficiency in buildings of all types. Experts have predicted that nearly 25% of possible reductions in CO2 emissions could result from relatively simple solutions such as improved insulation – so manufacturers and the roofing industry will see growing demand for solutions with minimal impact on the environment, both during manufacture and during their installed life.
As the search continues for viable, sustainable energy sources, the building industry has to do what it can to reduce the need for energy in the first place. On the other hand, the industry is also under pressure to deliver greater cost effectiveness and faster construction. This has driven increased demand for lightweight building materials which in turn mean that buildings now have a lower thermal mass. Lower thermal mass means that a building is more susceptible to daily temperature variations, making the building even more dependent on good insulation to avoid increasing the demand for artificial energy for heating or cooling.
While Part L of the Building Regulations is the primary driver for standards of energy efficiency in buildings, the cost of environmental correctness can be an issue for builders and their customers. Fortunately, cost effective solutions now available help to keep the heat in, reducing the demand for energy to provide more heat. One such solution is EcoTherm®’s Eco-Bond insulation board – which in addition to growing popularity in conventional roofing systems, is increasingly specified to complement green roof systems.
This product was used for 1,000m2 of eco-friendly roof – now spectacularly green – over the new Owners and Trainers Pavilion and conference centre at Chester Racecourse.
Eco-Bond boards are chosen for their low overall weight, high thermal performance to thickness ratio – and impressive green credentials of their own. With a lambda value of 0.026 W/mK Eco-Bond boards have less thermal conductivity than glass or mineral wool, making them ideal for applications where high levels of insulation are required. Every square metre of PIR has the potential, through improved energy efficiency, to save significant amounts of CO2 over the life of the building – and performance does not deteriorate, which is a disadvantage of some other types of insulation.
Eco-Bond from EcoTherm® is a closed cell rigid foam insulation board with a mineral-coated glass fibre tissue on both sides, designed for fully bonded single ply membrane systems, and also compatible with mechanically fixed systems. Eco-Bond is CFC and HCFC-free and has zero ozone depletion potential (ODP). It is available in thicknesses from 30-120mm – with the 120mm thickness providing a U-value of 0.20W/m2K on both metal and concrete decks. Eco-Bond is one of the leading roofboards in Europe, reflecting PIR’s unsurpassed record in the single ply roofing industry and high standards of performance under the most severe conditions of installation and use. When correctly installed, EcoTherm® Eco-Bond has an indefinite life. Its durability depends on the method of application, the supporting structure and the conditions of use.
In both conventional and green applications, EcoTherm® rigid insulation boards offer the highest rate of return per square metre, compared to other forms of insulation. They are recognised for their compressive strength, low weight, dimensional stability and ease of installation. Where necessary, to fit round projections through the roof for example, the boards are simply cut with a sharp knife or fine toothed saw. The PIR foam is chemically inert and safe to use.
Also popular for green roofs is EcoTherm®’s Eco-Fix, another ultra-lightweight PIR solution faced with aluminium foil on both sides, and designed for use with mechanically fixed single ply membranes. A 100mm Eco-Fix installation gives a U-value of 0.20W/m2K on metal decks. Eco-Fix, like Eco-Bond, is available in 1200mm widths and 2400mm lengths; Eco-Bond is also available in 600mm widths and 1200mm lengths.
Eco-Fix is used for the four apartment buildings and three restaurants – a total of 3,000m2 – in the Castle Quay development in Bedford, where they are topped with a single-ply membrane, filter matting and a green sedum roof, combining low growing grasses, mosses and alpine species, typically on a shallow substrate of 25-100mm.
Sedum roofs – one of the popular ‘extensive’ class of green roofs – are particularly popular because they are lightweight, adding no significant additional structural load on the building, and they require little or no maintenance. This means there is minimal foot traffic which might otherwise damage the insulation beneath the waterproofing membrane.
Other types of green roofs – such as the ‘intensive’ and ‘semi-extensive’ varieties – are constructed slightly differently, and are generally better suited to extruded polystyrene (XPS) insulation which is installed/ballasted over the waterproofing membrane. They accommodate wider diversities of plant species, but have a higher gardening maintenance requirement and need provision for more frequent access. On the whole they impose greater structural loads.
Installing a lightweight green roof based on a PIR insulation board from EcoTherm® creates no additional difficulties for either the specifier or the roofing contractor. The application should be treated in exactly the same way as a standard flat roof with adhered or mechanically fixed insulation and membrane. When the standard installation is complete and ready to perform to specification, simply add the ‘green’ elements to achieve the additional advantages of an eco-friendly roof.
We now have a substantial body of knowledge on insulation for green roofs – as we have for all our other product applications – and we are happy to provide technical backup for specifiers and contractors, so they can deliver maximum green benefits to end-users. Ironically, our latest PIR technology and expertise enable us to produce an effective ‘artificial’ insulation board: this permanent solution makes it possible for a ‘natural’ green roof to be considered.