Solid Wall Insulation - Regensw
RFR13
Solid Wall Insulation What is solid wall insulation? Solid walled properties are older homes, generally built before 1920’s which lose a significant amount of heat through their external walls compared to newer homes with insulated cavity walls. Heat is also lost through draughts moving through wall constructions, and here solid walls can be less draughty than even insulated cavity walls. Older solid walled homes nevertheless, tend to be cold and often more expensive to heat. Solid wall insulation (SWI) is an effective way of preventing this heat loss and can significantly reduce fuel bills and improve comfort conditions. To ensure solid wall insulation measures are able to deliver both fuel bill savings and allow for an increase in comfort (room temperatures) the level of insulation and draughtproofing should be carefully considered from the start. Solid walls can be insulated from the inside or the outside. The installation involves installing three basic measures: An insulation layer (which may incorporate separate structural support or other fixing methods) Draughtproofing and / or water vapour control layer(s) A protective, decorative finish In addition, when insulating internally, treatment may be required to reduce moisture movement at the base of walls without a damp proof course (DPC), and also an external treatment to improve the moisture handling characteristics of the existing wall may be recommended. Insulation can be externally and/or internally applied: External wall insulation (EWI) can allow higher overall levels of insulation and involves less technical risks than insulating internally Internal wall insulation (IWI) may often be the only practical solution for some or all walls, and insulation thickness is limited by room sizes and best practice limits - to avoid related technical risks.
Does SWI affect damp issues? Wall surface condensation forms when warm, moist air in the house comes into contact with a cold wall. SWI will provide warmer wall surfaces, limiting this type of surface condensation and the often seen resultant black mould growth.
EWI generally keeps most parts of the wall warm, however attention should be paid to any remaining cold spots that may be left, such as below DPC level at the base of the wall or at the point where EWI changes to IWI. Ideally the wall should be insulated down to the ground or even into the ground at wall bases, and internal insulation should overlap with external where possible to reduce these localised cold spots. Most external wall insulation systems using ‘open cell type’ allow water vapour to escape through both the insulation material and the microporous or fully ventilated weatherproof render or cladding. Less ‘vapour open’ insulations should be assessed for suitability by the installer. Ensuring adequate controllable house ventilation should always be part of any insulation improvement work.
How does SWI affect wall breathability? Adding insulation changes the ‘moisture balance’ of existing solid walls and particularly with internal insulation on exposed brick walls the use of ‘breathable’ brick treatments and ‘intelligent’ vapour control membranes should be considered to help manage any risks. Risks that may arise with poorly installed IWI include potential long term decay in timber joists close to or in the wall and hidden condensation and black mould growth or rot behind inadequately sealed internal insulation panels. Warm air escaping from a house passing through gaps in the wall (between floor and wall base at skirting level or around windows etc) carry hundreds of times more water vapour into wall constructions than water vapour diffusing through wall surfaces, so when fitting internal insulation it is important to ensure as many major gaps as possible are sealed in order to prevent these sort of heat losses but also to prevent this warm moist air from condensing and creating moisture related problems within the upgraded wall constructions. One of the major factors affecting the ‘moisture balance’ in the wall construction is how wet the external face of the masonry wall gets during rainy weather – a wetter wall loses more heat but also reduces the ability to allow any water vapour in the wall construction to evaporate from its surface. For example if sunshine falls on a wet soft brick wall water vapour may be driven backwards into the house through the wall construction (summertime condensation), this is where ‘variable vapour or intelligent membranes fitted internally can reduce the risk of condensation forming within the wall and creating moisture related risks). So adding a ‘microporous brick treatment’ creates a drier wall which loses both less heat and allows quicker drying from inside to out, whilst intelligent membranes also reduce ‘summertime condensation risk’ by safely allowing some drying back into the rooms.
Internal or external wall insulation? Both methods have advantages and disadvantages and a number of considerations need to be made before recommending one or the other including the following: budget ease of access aesthetic or planning considerations severity of heat loss from the property whether the home requires other repair work to interior or external walls
In some instances, a combination of the internal and external wall insulation may be the most appropriate solution; this is generally called a ‘hybrid’ insulation system (see below). Internal wall insulation (IWI) is done by fitting rigid insulation boards to the wall (that can be plastered or directly decorated), or by building a metal or timber stud wall filled with expanding spray foam, mineral or other suitable fibrous insulation material. IWI usually requires an air-vapour control layer on the warm side of the construction – in some situations there is a need to guard against ‘summer’ condensation risk within the IWI and ‘intelligent’ or ‘vapour-variable’ airvapour membranes may be used. It is important to seal this membrane to windows and doors to ensure adequate draughtproofing and vapour control. If windows are being replaced then the membrane should be sealed to the window frame and the IWI cover some of the window frame to improve thermal performance. Please guidance document RFR 15 on Internal Wall Insulation for more information. External wall insulation (EWI) involves fixing a layer of insulation material to the wall, then covering it with a thin but reinforced, waterproof but ‘breathable’ type of render (plasterwork). Alternatively a timber structure might be attached to the wall, filled with insulation and finished off with timber or other cladding (a ‘ventilated rain-screen’ approach). With EWI the finish can be varied, but the choice will be influenced also by what thickness can be accommodated, which in turn is affected by the thermal performance of the particular insulation used. If the associated draughtproofing relies on the outside face of the existing brick wall being ‘airtight’ then an initial thin covering of adhesive or render (known as ‘parging’) may be applied to the wall before the EWI is fixed. It is important to join this parging layer to windows and doors to ensure adequate draughtproofing and vapour control before EWI is applied – tapes or sealants may be used. If windows are being replaced then the EWI should cover some of the window frame to improve thermal performance. Please see guidance document RFR 14 on External Wall Insulation for more information. A hybrid system would incorporate internal or cavity insulation on some walls with external insulation on others. Hybrid systems can be very useful in instances where one type of insulation cannot be applied on every surface. In some situations SWI may involve cavity wall insulation, IWI and EWI. If a householders wants a high level of thermal improvement it may be more effective to ignore the cavity and treat the cavity wall as a solid wall use EWI – the draughtproofing layer (airtightness layer) should be the outside face of the existing wall as cavities leak air even when insulated (unless injected with closed cell expanding polyurethane type insulations which reduce air leakage via the cavity).
Does SWI have planning implications? For IWI planning permission is generally not required, unless you live in a listed building. For EWI planning permission may be required through the Local Planning Authority (LPA). The LPAs main considerations are usually whether the overcladding constitutes a change in visual appearance, including architectural details and effect on neighbouring properties. Properties in a conservation area will need to apply for planning permission. Local planning authorities can be found here.
Are there trade associations? We would recommend any company wanting to become a SWI installer joins a relevant trade association: Insulated Render & Cladding Association (INCA) National Insulation Association (NIA) British Rigid Urethane Foam Manufacturers’ Association (BRUFMA) Solid Wall Insulation Guarantee Agency (SWIGA)
Solid Wall Insulation What is solid wall insulation? Solid walled properties are older homes, generally built before 1920’s which lose a significant amount of heat through their external walls compared to newer homes with insulated cavity walls. Heat is also lost through draughts moving through wall constructions, and here solid walls can be less draughty than even insulated cavity walls. Older solid walled homes nevertheless, tend to be cold and often more expensive to heat. Solid wall insulation (SWI) is an effective way of preventing this heat loss and can significantly reduce fuel bills and improve comfort conditions. To ensure solid wall insulation measures are able to deliver both fuel bill savings and allow for an increase in comfort (room temperatures) the level of insulation and draughtproofing should be carefully considered from the start. Solid walls can be insulated from the inside or the outside. The installation involves installing three basic measures: An insulation layer (which may incorporate separate structural support or other fixing methods) Draughtproofing and / or water vapour control layer(s) A protective, decorative finish In addition, when insulating internally, treatment may be required to reduce moisture movement at the base of walls without a damp proof course (DPC), and also an external treatment to improve the moisture handling characteristics of the existing wall may be recommended. Insulation can be externally and/or internally applied: External wall insulation (EWI) can allow higher overall levels of insulation and involves less technical risks than insulating internally Internal wall insulation (IWI) may often be the only practical solution for some or all walls, and insulation thickness is limited by room sizes and best practice limits - to avoid related technical risks.
Does SWI affect damp issues? Wall surface condensation forms when warm, moist air in the house comes into contact with a cold wall. SWI will provide warmer wall surfaces, limiting this type of surface condensation and the often seen resultant black mould growth.
EWI generally keeps most parts of the wall warm, however attention should be paid to any remaining cold spots that may be left, such as below DPC level at the base of the wall or at the point where EWI changes to IWI. Ideally the wall should be insulated down to the ground or even into the ground at wall bases, and internal insulation should overlap with external where possible to reduce these localised cold spots. Most external wall insulation systems using ‘open cell type’ allow water vapour to escape through both the insulation material and the microporous or fully ventilated weatherproof render or cladding. Less ‘vapour open’ insulations should be assessed for suitability by the installer. Ensuring adequate controllable house ventilation should always be part of any insulation improvement work.
How does SWI affect wall breathability? Adding insulation changes the ‘moisture balance’ of existing solid walls and particularly with internal insulation on exposed brick walls the use of ‘breathable’ brick treatments and ‘intelligent’ vapour control membranes should be considered to help manage any risks. Risks that may arise with poorly installed IWI include potential long term decay in timber joists close to or in the wall and hidden condensation and black mould growth or rot behind inadequately sealed internal insulation panels. Warm air escaping from a house passing through gaps in the wall (between floor and wall base at skirting level or around windows etc) carry hundreds of times more water vapour into wall constructions than water vapour diffusing through wall surfaces, so when fitting internal insulation it is important to ensure as many major gaps as possible are sealed in order to prevent these sort of heat losses but also to prevent this warm moist air from condensing and creating moisture related problems within the upgraded wall constructions. One of the major factors affecting the ‘moisture balance’ in the wall construction is how wet the external face of the masonry wall gets during rainy weather – a wetter wall loses more heat but also reduces the ability to allow any water vapour in the wall construction to evaporate from its surface. For example if sunshine falls on a wet soft brick wall water vapour may be driven backwards into the house through the wall construction (summertime condensation), this is where ‘variable vapour or intelligent membranes fitted internally can reduce the risk of condensation forming within the wall and creating moisture related risks). So adding a ‘microporous brick treatment’ creates a drier wall which loses both less heat and allows quicker drying from inside to out, whilst intelligent membranes also reduce ‘summertime condensation risk’ by safely allowing some drying back into the rooms.
Internal or external wall insulation? Both methods have advantages and disadvantages and a number of considerations need to be made before recommending one or the other including the following: budget ease of access aesthetic or planning considerations severity of heat loss from the property whether the home requires other repair work to interior or external walls
In some instances, a combination of the internal and external wall insulation may be the most appropriate solution; this is generally called a ‘hybrid’ insulation system (see below). Internal wall insulation (IWI) is done by fitting rigid insulation boards to the wall (that can be plastered or directly decorated), or by building a metal or timber stud wall filled with expanding spray foam, mineral or other suitable fibrous insulation material. IWI usually requires an air-vapour control layer on the warm side of the construction – in some situations there is a need to guard against ‘summer’ condensation risk within the IWI and ‘intelligent’ or ‘vapour-variable’ airvapour membranes may be used. It is important to seal this membrane to windows and doors to ensure adequate draughtproofing and vapour control. If windows are being replaced then the membrane should be sealed to the window frame and the IWI cover some of the window frame to improve thermal performance. Please guidance document RFR 15 on Internal Wall Insulation for more information. External wall insulation (EWI) involves fixing a layer of insulation material to the wall, then covering it with a thin but reinforced, waterproof but ‘breathable’ type of render (plasterwork). Alternatively a timber structure might be attached to the wall, filled with insulation and finished off with timber or other cladding (a ‘ventilated rain-screen’ approach). With EWI the finish can be varied, but the choice will be influenced also by what thickness can be accommodated, which in turn is affected by the thermal performance of the particular insulation used. If the associated draughtproofing relies on the outside face of the existing brick wall being ‘airtight’ then an initial thin covering of adhesive or render (known as ‘parging’) may be applied to the wall before the EWI is fixed. It is important to join this parging layer to windows and doors to ensure adequate draughtproofing and vapour control before EWI is applied – tapes or sealants may be used. If windows are being replaced then the EWI should cover some of the window frame to improve thermal performance. Please see guidance document RFR 14 on External Wall Insulation for more information. A hybrid system would incorporate internal or cavity insulation on some walls with external insulation on others. Hybrid systems can be very useful in instances where one type of insulation cannot be applied on every surface. In some situations SWI may involve cavity wall insulation, IWI and EWI. If a householders wants a high level of thermal improvement it may be more effective to ignore the cavity and treat the cavity wall as a solid wall use EWI – the draughtproofing layer (airtightness layer) should be the outside face of the existing wall as cavities leak air even when insulated (unless injected with closed cell expanding polyurethane type insulations which reduce air leakage via the cavity).
Does SWI have planning implications? For IWI planning permission is generally not required, unless you live in a listed building. For EWI planning permission may be required through the Local Planning Authority (LPA). The LPAs main considerations are usually whether the overcladding constitutes a change in visual appearance, including architectural details and effect on neighbouring properties. Properties in a conservation area will need to apply for planning permission. Local planning authorities can be found here.
Are there trade associations? We would recommend any company wanting to become a SWI installer joins a relevant trade association: Insulated Render & Cladding Association (INCA) National Insulation Association (NIA) British Rigid Urethane Foam Manufacturers’ Association (BRUFMA) Solid Wall Insulation Guarantee Agency (SWIGA)
