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Nye typer betonelementer svarende til BR2005 energikrav

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In this project new solutions have been developed for buildings with concrete façade panels without ribs at window reveals and at horizontal joints, corresponding to panels with an un-broken insulation layer and limited thermal bridge effect. New general solutions for the mounting of windows have been developed together with airtight covering solutions at the window reveal based upon added window board and a separate vapor barrier. At the same time detailed calculations of the heat loss effects at the window-wall joint and foundation have been carried out and new solutions that reduce the heat loss substantially have also been shown.

The new developed standard solutions are obvious means to meet the expected future energy demands in the new Building Regulations expected in 2005. The project has revealed that it is possible to obtain significant thermal improvements with only a minor increase in the insula-tion thickness. The new and, in many ways, better solutions will mean added costs regarding mounting of windows, stronger fittings etc. but the effect of a standardization of the window-placement could reduce those additional costs considerably. The total life cycle costs regard-ing these new types of concrete façade panels are economically reasonable.

Window and doors

The starting point of the project has been to continue the development of solutions that are suitable for connecting windows and doors to concrete façade panels without ribs at the win-dow reveal. The background is that a satisfying low linear thermal transmittance around win-dows demands a thermal bridge break of about 100 mm, which frame constructions cannot cover and therefore it is reasonable to remove those ribs and cover the insulation with boards.

As part of the project a fitting system in steel for mounting of windows and doors has been developed. This has been put in production by BMF-SIMPSON and consists of consoles, side-fittings and diagonal-fittings – all anchored in the back wall. The system has been devel-oped for a window-placement at the outer wall, which is according to normal building prac-tice. The advantages are reduced risk of water intrusion and larger solar gains.

When the window is anchored at the back wall constrain forces due to temperature move-ments arise from deformation of the joint material between window and outer concrete layer. Calculations show that the problem is modest for storey high concrete panels where elastic joint material should be used, but for building high sandwich panels (used in industrial build-ings) and facing walls on multiple storey high buildings elastic joint material should be avoided and instead a solutions with less resistance against compression should be used (e.g. strip band).

Experience from today’s buildings where panels are built without ribs shows that joints be-tween window boards and window/panel seldom are airtight due to moisture- and temperature related movements. One recommendable solution is to use a moisture barrier from frame to the inside of the back wall, which is squeezed in the frame groove and at the back wall squee-zed into a cast in profile or through a profile mounted at the building site.

Empirically there are problems with incoming wind driven water above windows that need to be led out above the windows. One possible solution is a prefabricated element consisting of

two insulation triangles put together around a moisture barrier, which is placed immediately above the window, and a small flap is directed outwards to the joint above the window. Water tightness at the back wall can be established by making the panel 10 mm wider than the insu-lation thickness.

Joints between concrete panels

The traditional design of the horizontal joints between sandwich panels (the heel-toe-joint) is unnecessary to prevent percolation of water. Calculations and tests have shown that. In tests simulating a rather leaky wall-floor joint, only airborne drops of water can penetrate into the insulation, and only under extreme states of the wind. In the new solution the topside of the outer concrete layer is beveled with the inclination 1:2 and a mantle covers the insulation be-tween the two concrete layers. The mantle will shield the insulation against airborne drops of water, but primarily it shall lead out water that might have penetrated into the insulation. At the same time the mantle will shield the panel against percolation of water during storage in the panel factory, during transport and during the building period. The covering over vertical joints can be made by means of pieces of mantle glued across the joint to cover the vertical joint.

Linear thermal transmittance at window joints

Calculations have been made at the linear thermal transmittance in the window joint for the building–in of different typical types of windows into sandwich panels and panels with a fac-ing brick wall. These calculations generally show that the linear thermal transmittance will be relatively modest and on a level with the present standard requirements (0.03 W/mK) as long as the window is placed with normal joint against outer concrete layer/facing brick wall. If the window is fastened to the outer wall through a thickening or if the window is drawn right out into the façade, the heat flow behind the window will be increased considerably, and so will the linear thermal transmittance.

Calculations also show that the insulation thickness necessary to satisfy future outlined insula-tion requirements, with an assumed linear thermal transmittance of 0.03 W/mK and 1 m win-dow joint per m2 façade, is only about 200 mm, whereas there is a need for about 325 mm if a solution is used that comes up to the present minimum requirements (0.10 W/mK). It is there-fore absolutely crucial that the linear thermal transmittance is minimized. At a heat-technically optimal placing of the window straight in front of the insulation, the necessary in-sulation thickness is 165 mm.

Linear thermal transmittance at foundation

The linear thermal transmittance of typical foundations used in building is often significant, owing to the fact that the foundation for the sake of strength has to be made of massive concrete that has a relatively high thermal conductivity. The primary heat flow happens throgh the back wall and inside forundation part, and calculations show that a typical line loss is 0.40 W/mK, which is more than a factor two larger than typical single-family houses. It should be noticed that length of foundation compared to façade area are typically less than in single-family houses. It is possible to reduce the heat loss considerably by cutting off the primary heat flow using a combination of insulation and concrete as only about 20% of the inner concrete layer need to transfer the load. The heat loss could be reduced by 50% using 25 mm insulation under the inner concrete layer. By introducing insulation, an airthight joint is needed.

In industrial buildings with heavy loads on slap on ground, where it is impossible to use tradtional insulation, the floor construction is typically very badly insulated, which can result in line losses up to about 0.80 W/mK. Most buildings are heated up to more than 15 °C and a

good insulation is therefore desirable and demanded (demand in BR2005 is 0.40 W/mK). Calculations show that only a minor insulating layer in the floor construction, consisting of e.g. 100 mm loose light weight concrete aggregate combined with light weight concrete blocks in the foudation (between the load bearing columns), will reduce the heat loss significantly to around 0.30 W/mK.

In some cases the upper part of the foundation can be constructed in light weight concrete depending on the layout and purpose of the building. Typically it is possible in connection with small industrial buildings (3-5 m high, one storey building) with light roof and buildings in few storeys with concrete or light weight concrete back walls. Calculations show that the line loss can be reduced to 1/3 if the upper 60 cm of the foundation can be made of light weight concrete.

Industrial panels

Detailed heat loss calculations of building high sandwich panels used mainly in industrial buildings show that in general a U-value of 0.30 (minimum thermal insulation in proposal for energy demands in BR2005) can be optained with an insulation thickness at the ribs of approximately 60-70 mm, while it will be necessary with a ribinsulation of 125-140 mm to reduce the U-value to 0.18. For the last mentioned the corresponding insulation thicknesses will be 300-320 mm for load-bearing panels with side-ribs with the dimension 300 x 250 mm.

Thermal insulation

Heat loss calculations demonstrate that it is only necessary to increase insulation by 50 mm from approx. 150 to 200 mm in the new type of concrete façade panels to comply with the draft U-value of 0.18. If traditional solutions are used the insulation thickness has to be 350 to 500 mm.

Investment aspects and LCA

The cost comparison of traditional and new solutions shows that the biggest contribution to the added construction cost is the window mounting. When the standard solutions for mounting windows are incorporated it can be exspected that these exspences can be lowered considerbly compared to existing cost.

Cost calculations show that the new concrete façade panels increase the total construction cost by 5%, which is a modest additional cost compared to the saved heating costs. Life cycle cost calculations show that the net present value of investments and saved heating (timeframe of 30 years) is neutral or positive, depending on the economic scenario considered.

In general it can be concluded that it is possible for a smal additional cost to insure also large buildnings in the future as far as energy consumption is concerned.

Linear thermal transmittance at foundation

The linear thermal transmittance of typical foundations used in building is often significant, owing to the fact that the foundation for the sake of strength has to be made of massive concrete that has a relatively high thermal conductivity. The primary heat flow happens throgh the back wall and inside forundation part, and calculations show that a typical line loss is 0.40 W/mK, which is more than a factor two larger than typical single-family houses. It should be noticed that length of foundation compared to façade area are typically less than in single-family houses. It is possible to reduce the heat loss considerably by cutting off the primary heat flow using a combination of insulation and concrete as only about 20% of the inner concrete layer need to transfer the load. The heat loss could be reduced by 50% using 25 mm insulation under the inner concrete layer. By introducing insulation, an airthight joint is needed.

In industrial buildings with heavy loads on slap on ground, where it is impossible to use tradtional insulation, the floor construction is typically very badly insulated, which can result in line losses up to about 0.80 W/mK. Most buildings are heated up to more than 15 °C and a

good insulation is therefore desirable and demanded (demand in BR2005 is 0.40 W/mK). Calculations show that only a minor insulating layer in the floor construction, consisting of e.g. 100 mm loose light weight concrete aggregate combined with light weight concrete blocks in the foudation (between the load bearing columns), will reduce the heat loss significantly to around 0.30 W/mK.

In some cases the upper part of the foundation can be constructed in light weight concrete depending on the layout and purpose of the building. Typically it is possible in connection with small industrial buildings (3-5 m high, one storey building) with light roof and buildings in few storeys with concrete or light weight concrete back walls. Calculations show that the line loss can be reduced to 1/3 if the upper 60 cm of the foundation can be made of light weight concrete.

Industrial panels

Detailed heat loss calculations of building high sandwich panels used mainly in industrial buildings show that in general a U-value of 0.30 (minimum thermal insulation in proposal for energy demands in BR2005) can be optained with an insulation thickness at the ribs of approximately 60-70 mm, while it will be necessary with a ribinsulation of 125-140 mm to reduce the U-value to 0.18. For the last mentioned the corresponding insulation thicknesses will be 300-320 mm for load-bearing panels with side-ribs with the dimension 300 x 250 mm.

Thermal insulation

Heat loss calculations demonstrate that it is only necessary to increase insulation by 50 mm from approx. 150 to 200 mm in the new type of concrete façade panels to comply with the draft U-value of 0.18. If traditional solutions are used the insulation thickness has to be 350 to 500 mm.

Investment aspects and LCA

The cost comparison of traditional and new solutions shows that the biggest contribution to the added construction cost is the window mounting. When the standard solutions for mounting windows are incorporated it can be exspected that these exspences can be lowered considerbly compared to existing cost.

Cost calculations show that the new concrete façade panels increase the total construction cost by 5%, which is a modest additional cost compared to the saved heating costs. Life cycle cost calculations show that the net present value of investments and saved heating (timeframe of 30 years) is neutral or positive, depending on the economic scenario considered.

In general it can be concluded that it is possible for a smal additional cost to insure also large buildnings in the future as far as energy consumption is concerned.

Linear thermal transmittance at foundation

The linear thermal transmittance of typical foundations used in building is often significant, owing to the fact that the foundation for the sake of strength has to be made of massive concrete that has a relatively high thermal conductivity. The primary heat flow happens throgh the back wall and inside forundation part, and calculations show that a typical line loss is 0.40 W/mK, which is more than a factor two larger than typical single-family houses. It should be noticed that length of foundation compared to façade area are typically less than in single-family houses. It is possible to reduce the heat loss considerably by cutting off the primary heat flow using a combination of insulation and concrete as only about 20% of the inner concrete layer need to transfer the load. The heat loss could be reduced by 50% using 25 mm insulation under the inner concrete layer. By introducing insulation, an airthight joint is needed.

In industrial buildings with heavy loads on slap on ground, where it is impossible to use tradtional insulation, the floor construction is typically very badly insulated, which can result in line losses up to about 0.80 W/mK. Most buildings are heated up to more than 15 °C and a

good insulation is therefore desirable and demanded (demand in BR2005 is 0.40 W/mK). Calculations show that only a minor insulating layer in the floor construction, consisting of e.g. 100 mm loose light weight concrete aggregate combined with light weight concrete blocks in the foudation (between the load bearing columns), will reduce the heat loss significantly to around 0.30 W/mK.

In some cases the upper part of the foundation can be constructed in light weight concrete depending on the layout and purpose of the building. Typically it is possible in connection with small industrial buildings (3-5 m high, one storey building) with light roof and buildings in few storeys with concrete or light weight concrete back walls. Calculations show that the line loss can be reduced to 1/3 if the upper 60 cm of the foundation can be made of light weight concrete.

Industrial panels

Detailed heat loss calculations of building high sandwich panels used mainly in industrial buildings show that in general a U-value of 0.30 (minimum thermal insulation in proposal for energy demands in BR2005) can be optained with an insulation thickness at the ribs of approximately 60-70 mm, while it will be necessary with a ribinsulation of 125-140 mm to reduce the U-value to 0.18. For the last mentioned the corresponding insulation thicknesses will be 300-320 mm for load-bearing panels with side-ribs with the dimension 300 x 250 mm.

Thermal insulation

Heat loss calculations demonstrate that it is only necessary to increase insulation by 50 mm from approx. 150 to 200 mm in the new type of concrete façade panels to comply with the draft U-value of 0.18. If traditional solutions are used the insulation thickness has to be 350 to 500 mm.

Investment aspects and LCA

The cost comparison of traditional and new solutions shows that the biggest contribution to the added construction cost is the window mounting. When the standard solutions for mounting windows are incorporated it can be exspected that these exspences can be lowered considerbly compared to existing cost.

Cost calculations show that the new concrete façade panels increase the total construction cost by 5%, which is a modest additional cost compared to the saved heating costs. Life cycle cost calculations show that the net present value of investments and saved heating (timeframe of 30 years) is neutral or positive, depending on the economic scenario considered.

In general it can be concluded that it is possible for a smal additional cost to insure also large buildnings in the future as far as energy consumption is concerned.

Linear thermal transmittance at foundation

The linear thermal transmittance of typical foundations used in building is often significant, owing to the fact that the foundation for the sake of strength has to be made of massive concrete that has a relatively high thermal conductivity. The primary heat flow happens throgh the back wall and inside forundation part, and calculations show that a typical line loss is 0.40 W/mK, which is more than a factor two larger than typical single-family houses. It should be noticed that length of foundation compared to façade area are typically less than in single-family houses. It is possible to reduce the heat loss considerably by cutting off the primary heat flow using a combination of insulation and concrete as only about 20% of the inner concrete layer need to transfer the load. The heat loss could be reduced by 50% using 25 mm insulation under the inner concrete layer. By introducing insulation, an airthight joint is needed.

In industrial buildings with heavy loads on slap on ground, where it is impossible to use tradtional insulation, the floor construction is typically very badly insulated, which can result in line losses up to about 0.80 W/mK. Most buildings are heated up to more than 15 °C and a

good insulation is therefore desirable and demanded (demand in BR2005 is 0.40 W/mK). Calculations show that only a minor insulating layer in the floor construction, consisting of e.g. 100 mm loose light weight concrete aggregate combined with light weight concrete blocks in the foudation (between the load bearing columns), will reduce the heat loss significantly to around 0.30 W/mK.

In some cases the upper part of the foundation can be constructed in light weight concrete depending on the layout and purpose of the building. Typically it is possible in connection with small industrial buildings (3-5 m high, one storey building) with light roof and buildings in few storeys with concrete or light weight concrete back walls. Calculations show that the line loss can be reduced to 1/3 if the upper 60 cm of the foundation can be made of light weight concrete.

Industrial panels

Detailed heat loss calculations of building high sandwich panels used mainly in industrial buildings show that in general a U-value of 0.30 (minimum thermal insulation in proposal for energy demands in BR2005) can be optained with an insulation thickness at the ribs of approximately 60-70 mm, while it will be necessary with a ribinsulation of 125-140 mm to reduce the U-value to 0.18. For the last mentioned the corresponding insulation thicknesses will be 300-320 mm for load-bearing panels with side-ribs with the dimension 300 x 250 mm.

Thermal insulation

Heat loss calculations demonstrate that it is only necessary to increase insulation by 50 mm from approx. 150 to 200 mm in the new type of concrete façade panels to comply with the draft U-value of 0.18. If traditional solutions are used the insulation thickness has to be 350 to 500 mm.

Investment aspects and LCA

The cost comparison of traditional and new solutions shows that the biggest contribution to the added construction cost is the window mounting. When the standard solutions for mounting windows are incorporated it can be exspected that these exspences can be lowered considerbly compared to existing cost.

Cost calculations show that the new concrete façade panels increase the total construction cost by 5%, which is a modest additional cost compared to the saved heating costs. Life cycle cost calculations show that the net present value of investments and saved heating (timeframe of 30 years) is neutral or positive, depending on the economic scenario considered.

In general it can be concluded that it is possible for a smal additional cost to insure also large buildnings in the future as far as energy consumption is concerned.