Happy Valley Posted April 1, 2021 Share Posted April 1, 2021 I have been provided with the following information as part of the SAP for our 160 sq m new build: This is the initial draft for the design Summary of input data Basement floor and Ground floor 0.13W/m²K Basement wall and Main wall 0.2W/m²K Roof 0.13W/m²K Thermal bridging - used ICF details and PSI values where possible Windows u value 1.4W/m²K G factor 0.63 Doors u value 1.4W/m²K Ventilation MVHR Envirovent energiSava 380 extract to Kitchen + 4 other rooms (assumption only because the SAP default is not compliant with building regs. this can be updated when the proposed is known) Air tightness 4.0 m³/hm² (I have kept this quite low because it enhances the MVHR performance and ICF is naturally air tight) Main heating, Generic ASHP supplying underfloor heating with time and temperature zone control. Design flow temperature 35ºC Secondary heating - none Water heating - 250 litre cylinder with losses of 1.67 kWh/day from heat pump 100% low energy lighting With this information is there a way of working out what sized ASHP is required? Link to comment Share on other sites More sharing options...
JamesP Posted April 1, 2021 Share Posted April 1, 2021 Couple of threads here. Link to comment Share on other sites More sharing options...
PeterW Posted April 1, 2021 Share Posted April 1, 2021 51 minutes ago, Happy Valley said: I have been provided with the following information as part of the SAP for our 160 sq m new build: This is the initial draft for the design Summary of input data Basement floor and Ground floor 0.13W/m²K Basement wall and Main wall 0.2W/m²K Roof 0.13W/m²K Thermal bridging - used ICF details and PSI values where possible Windows u value 1.4W/m²K G factor 0.63 Doors u value 1.4W/m²K Ventilation MVHR Envirovent energiSava 380 extract to Kitchen + 4 other rooms (assumption only because the SAP default is not compliant with building regs. this can be updated when the proposed is known) Air tightness 4.0 m³/hm² (I have kept this quite low because it enhances the MVHR performance and ICF is naturally air tight) Main heating, Generic ASHP supplying underfloor heating with time and temperature zone control. Design flow temperature 35ºC Secondary heating - none Water heating - 250 litre cylinder with losses of 1.67 kWh/day from heat pump 100% low energy lighting With this information is there a way of working out what sized ASHP is required? That’s a pretty crap window score - most modern UPVC hits 1.0 without a huge issue so why go with a lower performance ..?? Basement/ground floor is too high as well - get them to 0.11 or 0.1 using slightly better insulation and you will get much better SAP score and lower run costs. Link to comment Share on other sites More sharing options...
SteamyTea Posted April 1, 2021 Share Posted April 1, 2021 ACH is poor to. Link to comment Share on other sites More sharing options...
SteamyTea Posted April 1, 2021 Share Posted April 1, 2021 1 hour ago, Happy Valley said: With this information is there a way of working out what sized ASHP is required Yes get some local weather data and it becomes easy 1 Link to comment Share on other sites More sharing options...
Happy Valley Posted April 1, 2021 Author Share Posted April 1, 2021 2 hours ago, PeterW said: That’s a pretty crap window score - most modern UPVC hits 1.0 without a huge issue so why go with a lower performance ..?? Basement/ground floor is too high as well - get them to 0.11 or 0.1 using slightly better insulation and you will get much better SAP score and lower run costs. Thanks for your input. Since this was done I have a quote for Velfac windows with a U of 0.79 to 0.82. Shall discuss the ground floor with the architect. Link to comment Share on other sites More sharing options...
Moonshine Posted April 1, 2021 Share Posted April 1, 2021 2 hours ago, SteamyTea said: get some local weather data and it becomes easy what sort? monthly averages? Link to comment Share on other sites More sharing options...
J1mbo Posted April 1, 2021 Share Posted April 1, 2021 degree days Link to comment Share on other sites More sharing options...
SteamyTea Posted April 1, 2021 Share Posted April 1, 2021 2 minutes ago, Moonshine said: what sort? monthly averages? Daily if you cannot find hourly. Ideally Temperature, Solar, RH, Windspeed and Direction. Link to comment Share on other sites More sharing options...
Iceverge Posted April 1, 2021 Share Posted April 1, 2021 Without know the various areas of your windows walls and doors it's impossible to say. A 160m2 bungalow has a far greater surface area than a 2.5 story cube. Either that or forego the ASHP at build stage. Install a wills heater and monitor it for a year. You'll know exactly then. Link to comment Share on other sites More sharing options...
ProDave Posted April 1, 2021 Share Posted April 1, 2021 You don't need a whole years worth of data do size an ASHP. You just need to know the buildings heat loss at the coldest temperature you expect to have to deal with in a normal winter. I based that on -10 outside for where we live. The heat loss is so low, the smallest ASHP we could find gives twice the amount of heat we need even in the depths of winter. Link to comment Share on other sites More sharing options...
J1mbo Posted April 1, 2021 Share Posted April 1, 2021 Quick calc suggests required DHW reheat time is likely to be the key sizing requirement for this property. Link to comment Share on other sites More sharing options...
Happy Valley Posted April 2, 2021 Author Share Posted April 2, 2021 18 hours ago, Iceverge said: Without know the various areas of your windows walls and doors it's impossible to say. A 160m2 bungalow has a far greater surface area than a 2.5 story cube. Either that or forego the ASHP at build stage. Install a wills heater and monitor it for a year. You'll know exactly then. House is stepped up a slope but about 98 sq m is effectively at ground level. The wills heater intrigues me and if we can get the U values down enough will certainly consider it. Do they have a maximum floor area for UFH? Link to comment Share on other sites More sharing options...
Iceverge Posted April 2, 2021 Share Posted April 2, 2021 you can add more than one if needed. your peak heating load is what you’re after. there’s a good spreadsheet here somewhere if you search for it. 1 Link to comment Share on other sites More sharing options...
Moonshine Posted April 12, 2021 Share Posted April 12, 2021 45 minutes ago, SolarSunScott said: I have an MCS spreadsheet I can email you. I inboxed you my email do you mind sending it to me? Link to comment Share on other sites More sharing options...
Moonshine Posted April 12, 2021 Share Posted April 12, 2021 3 minutes ago, SolarSunScott said: what is your email address? you can send the excel file via the forum message service Link to comment Share on other sites More sharing options...
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