an introduction to hydronic underfloor heating
Contents
1. being discussed and will be different in every installation temperature which increases running costs if a single heat pump is used A more expensive alternative is to use multiple heat pumps running at different temperatures This is sometimes used for larger homes or use supplementary heating in hard to heat rooms Heat loss from glazed areas In a new house around 50 of the heat loss is through Heat loss per square meter of external surface W C m glazing alone This is because 0 1 2 3 4 5 standard aluminium framed double glazing loses heat at nearly 8 times the rate of a standard insulated wall See chart below Roof NZBC minimum Floor NZBC minimum Wall NZBC minimum Uninsulated weather board wall Window double low e wood or A highly glazed room will have much more heat loss per square meter than the average heat loss for the house As the heat flow from the floor is limited by i the surface temperature it is Window Single clear possible even in a new house to design a room with a heat loss exceeding the heat that can be delivered by an underfloor system particularly if a heat pump is used which limits operating temperature Window Double low e curtains Window Double low e Window Double clear curtains Window Double clear Such rooms often need a supplementary heat source to maintain temperature in very cold weather Alternatively the thickness of floor coverings needs to2. vary greatly according to the size of house and lifestyle Running costs for different fuels based on 20 000 kWh heat load which could include potable hot water or other heat loads such as swimming pools Costs calculated January 2012 for Christchurch NG for Auckland Unit heating cost cents kWh Baxi high efficiency gas boiler NG 1 801 p90 Baxi high efficiency gas boiler LPG 3 489 Firebird Enviromax diesel boiler 3 004 Heat source Annual heating cost Assumptions made about electricity pricing No daily fixed charge is included in costings for single phase supplies as it is assumed this would be paid anyway even without electrical heating A prompt payment discount of 10 is applied Cost estimates are for single phase power only 3 Phase Electricity For a heat pumps with an output greater than 14kW a three phase model would be needed The cost of connecting three phase power to a site that wouldn t otherwise have it needs to be taken into account The tariff is likely to be commercial with a larger fixed cost element and reduced unit charge compared to a standard domestic tariff The connection and running costs will be particular to the site so it is not possible to give generalised advice It is possible to used single phase to three phase converters or more than one single phase heat pump on site provided the total power kW drawn doesn t exceed the total power available for the site What level o
3. floor thought needs to be given to where cuts are made and how this might impact on the pipes in the floor This won t be a problem as long as the heating installer and builder can work together to make sure the heating system isn t compromised There are alternative systems to cutting which avoids any problems that might occur Some are crack inducing systems that are laid at the underside of the slab such as the product shown in this picture right Expansion Joints An alternative is to use expansion joints such as the ones shown right When these are used it is important the pipes are laid before the joint is fixed in place otherwise laying the pipe underneath will be very difficult Screed floors The mix of the screed needs to be correct to prevent cracking CHNZ can provide a specification on request Where edge insulation is used to prevent heat leaking out from the heated slab as used in European screed and micro screed systems the insulation will not provide a good fixing around the edge of a floor For practical reasons it is normal to cover the top of the edge insulation with the skirting board which is made the same thickness as in the diagram below Wine cellars Many homes these days have a wine cellar which is often a small room rather than a real cellar Designers need to be aware that even if the floor in that room doesn t have pipes in it the room will still be heated by the heat spreadi
4. means door heights etc will be reduced unless spreader plates are used under a timber floor Underfloor Heating Methods 1 In slab Kiwi underfloor heating The most commonly used form of central heating in New Zealand Pipes are laid on polystyrene insulation or attached to reinforcing mesh Concrete is poured over the mesh and insulation These concrete slabs are usually between 100 150mm in thickness Advantages Relatively inexpensive and simple to install Large thermal mass retains heat Disadvantages Whilst thicker slabs mean greater thermal mass they also mean they are not as quick to heat should they lose temperature 3 Multitubo micro screed A much thinner system using smaller pipes laid into a special moulded floor plate A screed thin layer of concrete is spread over the pipes with the flooring then laid on top of this Due to its low weight and height this method is suitable for installing over existing timber floors as well as concrete floors Advantages Much thinner than a standard system which reduces thermal mass and minimises increase in floor height in retro fitted properties Disadvantages More expensive to lay than the basic in slab system 2 European screed underfloor heating Usually around 50mm thick it has reduced thermal mass compared to in slab and is totally insulated from the rest of the building and the outside meaning much lower losses higher efficiency and faster resp
5. AN INTRODUCTION TO HYDRONIC UNDERFLOOR HEATING a concise guide for architects amp specifiers on planning underfloor heating systems qe WNT L 3 He Ux if Contents Underfloor heating the ultimate in comfort amp design 3 Underfloor Heating Methods 5 Can underfloor heating be used with radiators on the same system 6 Choices of Heat Sources 7 What are the running costs like for an underfloor heating system 8 What level of control is there in a hydronic underfloor heating system 9 Design amp installation issues to consider when planning underfloor heating 10 Design amp installation process for in slab amp Screed underfloor heating systems 16 Our Expertise 17 Underfloor heating the ultimate in comfort amp design Luxurious silent amp discrete Underfloor heating is the most luxurious form of heating as radiant heat is evenly distributed throughout the room wall to wall floor to ceiling Hard floor surfaces are warm to the touch this is very important with increased numbers of new houses being built with concrete floor surfaces And the system is totally hidden from view and takes up no wall space very important to many people especially where large glazed areas mean there is little or no wall space With no air being blown around it is totally Silent The heat can be provided by specially designed air to water heat pumps or by boilers fuelled by gas diesel or
6. E EAEn Mk A centrally placed manifold uses the house results in a hot track of concentrated pipes running down the passage providing heat where it is least needed and the two bedrooms at the other end of the house needing two pipe loops in each room aa Bad manifold placement 20 less pipe and 20 less pipe laying labour costs and two less loops to plumb in and there is no hot track so the heat is more evenly distributed Good manifold placement Floor coverings Effect of floor coverings on operating temperature to achieve a Any floor covering on top of the floor surface temperature of 25 C and air temperature of 20 C heated part of the floor acts as a barrier to the heat flowing from the floor into the room Thicker floor ee Heat coverings such as carpet can be used Carpet with but the heating system has to be run He at a higher temperature to get the required heat output which is less efficient if a heat pump is used Concrete 25 C floor Hs 35 C 1 If the operating temperature has to be raised just for one room the whole PALER IA A REE EIE Ee house will have to run at a higher NB The temperatures in this drawing are chosen to illustrate the concept
7. at pump or boiler if outside and fuel supply if needed FINAL FIX Heat source pumps etc installed Controls installed Fuel tank installed if needed System commissioned amp tested System hand over to customer accompanied by user manual Design Stage Installed by builder Installed by CHNZ SCREED FLOOR HEATING DESIGN STAGE agreement needed on e Manifold and heat source positions e Position of thermostats and floor probes Draining for condensate e Water supply point for system filling Perimeter walls are built with penetrations Builder marks for pipework out positions of heat source l l amp manifolds Primary pipe work from heat source to manifolds is installed l Builder marks Shingle poured DPM under slab insulation out positions mesh on chairs of manifolds amp walls Walls amp roof erected Insulation installed under screed pipe Loops fixed to Insulation Loops pressure tested Screed poured Cabinets and manifolds installed at pre pipe stage l Control wiring and power to heat source installed at wiring stage Slab poured for heat pump or boiler if outside and fuel supply if needed FINAL FIX Heat source pumps etc installed Controls installed Fuel tank installed if needed System commissioned amp tested System hand over to customer accompanied by user manual Our Expertise Design excellence the Central Heating New Zealand difference At Centra
8. be minimised 11 Design amp installation issues to consider when planning underfloor heating cont Timber amp heated floors To avoid cracking it is recommended that only properly dried timber is used or a timber floor product with an MDF backing or similar Despite these issues it is very common to have timber coverings on heated floors with no problems at all It is preferable to glue timber to a concrete slab or screed and not to use foam backing Wall positioning and fixings to floor slab Before the floor pipe loops are installed for a basic in slab system the builder will need to mark out the position of the walls as it is usual to run the pipes to avoid going under walls so that the pipes are not punctured by fixings into the floor In this picture right the wall positions are marked in yellow and the pipe loop in the room goes in and out of the acl doorway 7 gf a EE EF ae 05 i A common cause of pipes being gt Sea a punctured is when wall positions Da are changed after the slab has been poured and are put over pipe runs This only applies to the basic in slab method It is often preferable to have the pipes from a manifold radiating out either side of a wall This requires the cooperation of all involved to make sure that part of the wall is not fixed into the floor slab where the pipes come into the manifold Concrete crack inducement and concrete cutting If you are having a polished concrete
9. e system is large and so it takes a long time to heat up the E Zone4 floor slab With these systems the slab becomes a heat Zone 5 store Controllers for high thermal mass systems monitor the actual floor slab temperature to keep it within a certain temperature range to improve response time When using a heat pump it is often only the temperature of the slab that is controlled by running the heat pump continuously at a fixed setpoint When the house is heated by the sun and the room temperature rises the temperature difference between the slab and room is reduced and so the heat transfer becomes minimal To a large extent underfloor heating can be self regulating without the need fora room thermostat Design amp installation issues to consider when planning underfloor heating Manifold placement Manifolds are a key part of the system and need to be placed as centrally as possibly for optimal performance Usually they are at the back of cupboards or in the laundry Badly placed manifolds result in much more pipe being laid which adds to material and labour costs If there is one manifold at one end of the house pipes needs to be run to the other end of the house and back reducing the length of pipe in the area being heated by that particular loop This also produces a hot floor usually in the hallway where heating is least needed Underfloor manifolds are not a decorative feature and need to be hidden however simply putt
10. erature or two heat pumps used one for the underfloor and a high temperature model for the radiators Incorporating underfloor into a radiator system If a system is mostly radiators it is possible to have a small area of underfloor running through a return temperature limiting valve This can cover about 15m2 per valve This is a specifically designed thermostatic valve that allows the floor to be heated via higher temperature water but limits how hot it can get Choices of Heat Sources Runs on your preferred fuel no matter where you are Underfloor heating can use heat pumps or boilers for supplying heat Often the heat source is determined by the availability of fuels in the area Heat pumps work very efficiently and have low running costs at the lower operating temperatures of underfloor typically 40 C compared to radiators typically 70 C High efficiency condensing boilers also run more efficiently at lower operating temperatures Unless a Baxi gas boiler is used which has a special underfloor setting a mixing valve is needed to reduce the temperature of the water going into the floor What are the running costs like for an underfloor heating system Running costs are a key issue for clients and one which can be very difficult to answer due to the variability in types of fuels and prices around New Zealand It is fairly easy to estimate unit running costs for different heat sources but annual totals
11. f control is there ina hydronic underfloor heating system Heating controls allow central heating systems to run totally automatically with virtually no input from the user other than to change or temporarily override the program This is a major attraction of central heating as the house is always warm when you get up in the morning no matter what the weather with minimal input from the users The basic functionality of the control system is to switch the heat source on and off and to direct the heat to where it is needed by opening and closing valves and or switching pumps on and off Each system is designed according to the occupant s personal preferences Some people prefer to run the system continuously all winter only controlling the temperature of the water going into the floor whilst others have thermostats in each room to precisely control the temperature according to a time schedule w Garage Multi zone control It is possible to create different zones within a house which are automatically heated to different temperatures at different times but can still be overridden manual when a variation to the schedule is needed Having separate thermostats and time schedules for each room can make for a very complex control system and potentially confusing if the owners haven t had central heating before Slab temperature and response rate Master The thermal mass of a heated slab or European screed aa W
12. ing them out in the garage may well result in a poorer performing system A better result for the customer is to find or create space for a manifold cabinet In this case the manifold cabinet is inset into the wall reducing space taken up and allowing pipes to leave the manifold in either direction which is usually better than from one side only Manifold cabinets Height 600mm depth 130mm Length depends on number of loops and whether a mixing valve is used or not pnm a Le P eae Manifold J EO
13. l Heating New Zealand we believe that good design should be at the heart of any heating system That s why each underfloor system design starts with a heat loss calculation something absolutely essential in ensuring the finished system will heat to the temperature and comfort level required To ensure that each of our system performs to exacting standards Central Heating New Zealand employs qualified heating engineers and uses state of the art Computer Aided Design tools to produce designs for residential and commercial properties About Central Heating New Zealand Central Heating New Zealand is the country s leading hydronic heating specialist offering a full range of heat pump and boiler radiant systems to the public and to trade customers nationwide Central Heating New Zealand is certified with the International Ground Sourced Heat Pump Association and has more than 40 geothermal heating systems installed and operated across New Zealand For more details on this or any of our products contact us on 03 357 1233 or email enquiries centralheating co nz Alternatively you can find out more about us and our products at centralheating co nz or viewing our product pages on productspec net Central Heating NEW ZEALAND PO Box 31 274 52 Pilkington Way Wigram Christchurch 8042 Tel 03 357 1233 Fax 03 343 1236 enquiries centralheating co nz www centralheating co nz
14. ng through the concrete slab from heated areas Design amp installation issues to consider when planning underfloor heating cont Thermal Bridging When using an existing building element as a heat emitter in this case the floor there is a danger eg iii soe Fan that heat loss to the outside can be greater than normal due to thermal bridging This is caused by higher conductivity materials such as concrete running continuously between the inside and outside of the building creating a path for heat to flow out This mainly happens with pipes ot ee Blinding amp inset into the main floor slab as Er se hardfill other methods tend to be thermally 1 isolated from the outside of the house Pipes set in main slab Use treated timber i l Heat flows from the main slab Aletas thermdi ek pol E through the concrete to the outside 50mm softwood Fig 1 above right R 0 42 To counter this heat loss BRANZ recommend using a thermal break of timber between the main slab and the outer foundation Fig 2 right Screed floors fig 3 below right go one step further by having a completely insulated surface slab cutting out heat loss through the siting pered iy slab edge entirely board insulated from surrounding structure Further options for insulating insulation around floor slabs can be found in the BRANZ Insulation Guide 14 The following examples show other situations where thermal bridging increase
15. onse to controls Can be used for retrofit if the existing floor is strong enough and the raised floor level is acceptable Advantages More efficiency and faster response to controls Loses less heat through edge of the slab Disadvantages More expensive than basic in slab underfloor due to the two layers of concrete and greater amount of insulation 4 Metal plate timber floor system Alloy plates to spread heat are laid under floor boards or timber panel floors The pipes are clipped into the plates which conduct the heat away from the pipes Insulation is positioned under the plates and pipes Advantages Enables underfloor heating for timber floors without raising the floor level in existing buildings or building a floor to support a heavy screed in a new building Disadvantages More expensive to lay than the basic in slab floor Can underfloor heating be used with radiators on the same system Incorporating radiators into an underfloor system Radiators and underfloor can be and are often used in the same system Usually with the living areas kitchen and bathrooms hard floor areas in underfloor and the bedrooms with radiators This is easy to accomplish with a boiler as it can supply high temperature water to the radiators and heat the floor via and thermostatic valve to reduce the temperature of the water going into the floor If a heat pump is used the radiators will have to be sized to run at a lower temp
16. s heat loss it will still be possible to heat the house but more energy will be used Concrete Deck If a concrete deck abuts a heated floor slab there will inevitably be some heat conducted through to the outside Tilt slab or concrete block walls If the heated floor slab abuts a concrete exterior wall there will be enhanced heat transfer to the outside Unheated space below floor slab If a heated floor slab has an unheated space below it it must be insulated not only below the slab but around any supporting beams Any block wall supporting the heated Slab will also conduct heat away to the outside Inside Outside Heated floor slab Insulation on inside of wall Fa Outside f Inside Outside Heated floor slab Design amp installation process for underfloor heating systems IN SLAB HEATING DESIGN STAGE agreement needed on e Manifold and heat source positions Position of thermostats and floor probes e Draining for condensate e Water supply point for system filling Perimeter walls are built with penetrations for pipework Primary pipe work from heat source to manifolds is installed Shingle poured DPM under slab insulation mesh on chairs Pipe loops installed fixed to mesh Loops pressure tested l Slab poured Cabinets and manifolds installed at pre pipe stage Control wiring and power to heat source installed at wiring stage Slab poured for he
17. wood The floor can be heated either by electric elements under the floor covering or by hot or warm water being pumped through pipes inside the floor also known as hydronic heating This guide is only concerned with hot water pipe hydronic underfloor heating systems Energy efficient Underfloor systems can run at much lower temperatures than radiator systems which increases the efficiency of the boilers and heat pumps used to supply the heat How does underfloor heating work The heat source A boiler or heat pump supplies heat to the system by heating the water Boiler aD that is pumped through it P Primary pipework carries the Pump Controls from heat from the heat source to the very simple to one manifold s in every room Manifolds distribute the heat to the underfloor pipe loops Manifold in cabinet Pipe loops with hot water flowing through them heat the floor typically at least 1 loop boia for every 20m2 of heated floor Oi JII area 8 TT Controller switches the heat Thermostatic valve source on and off and directs Boilers only gt More loops the heat to where it is needed to heat the rooms to the desired temperature Pipe loops set into floor Can underfloor heating be installed in my home Retro fit to ild Heating Method NE ERIE existing home Alloy plate system for timber joist floors When underfloor is retrofitted the floor level will be raised which
Download Pdf Manuals
Related Search