In-depthness - LOL, good video series. This hopefully will get super popular with rising energy prices and customers will start asking their installers the right questions.
A word of caution on the numbers on the cheat sheet. They are for a "typical" house (I assume two storey detached?). Different house "formats" can vary significantly as to the ratio of house "envelope" to floor space and this can greatly skew the numbers. For example, bungalows typically have significantly more exterior surface per square meter of floor space than two storey houses (I have an L shaped bungalow, and that has even more, with the two largest rooms each having 3 exterior walls). Mid-terrace houses can have a lot less effective envelope - the party walls really being more like internal walls than external walls. Semis/end-of-terraces are somewhere between detached and terraced. As is said, you can't miss out on the detailed heat loss calc for your home.
You might have told me this a few weeks ago before I measured EVERYTHING! Your cheat sheet is spot on :) presumably if I need 27kwh for heating then I'd need enough heat pumps that match that output? Eeek.
Love it , videos like this are a must for the end customers/homeowners, to start to understand what they are using / what they need to invest into reduce their heating bills, could just get the heating professional to fit better controls and commission their existing boiler and system to use as little heat/fuel as possible,
Ok, so here's my issue with these kind of topics, and please give me your input as I would be interested to hear your take on this point of view. THE most popular boiler type in the UK is without doubt a condensing combination boiler, and for many reasons. The most popular being their versatility of not requiring stored hot water, for which a hell of a lot of homes in the UK benefit from this as space in most average 2-3 bedroom family homes is lacking. Now here's my point, most smaller Combi's are around the 24kw range, which in your eyes is overkill for most UK homes in terms of heat loss, and I would agree. BUT, as I said, space is often very limited, so a cylinder and a lower KW S Boiler or Heat only boiler is out of the question. Then we have to factor in that 3 bed family homes may have as many as 6 people in that house, for which a good HW flow rate is needed. We can only get greater flow rates from larger combi's starting from about 33KW right through to 40+KW combi's. Otherwise we as installers get very dissatisfied customers that are constantly on the phone complaining that HW performance is terrible. I've tried putting this point across on a couple of other channels and get accused of being a lazy installer that doesn't understand how to design systems, and this is not the case at all. You can go on most ex council estates in the UK and find either 1; there's no reasonable amount of space for a conventional/unvented installation 2; The customer doesn't want to pay the extra for that kind of installation or 3; just doesn't want a HW store period. Sorry for the long post but it is a real issue real world installers face and more often than not, were backed against a wall.
Of course! If they can't have a tabk they can't have a heat pump.. we tell loads of customers they can't have them for many reasons.. we're saying they work where they work.. not "they work everywhere".. gas boilers don't work on the 20% of the country that's of grid. . However the sunamp does get around this space issue very often as they're tiny.. and square...
@@ChapmanPlumbing yes my main point was regarding boilers not ASHP. And in terms of fitting a cylinder in a loft, that's fine for smaller families with only maybe one child, but it doesn't last long when everyone is using it in a home with 2 or more children. You have to wait for it to heat up again after running a bath or when the wife or teenager take 20minute showers. I'm not saying your points are wrong or anything like that, but nobody ever puts videos out discussing why so often heating engineers install larger boilers. It's not for laziness (although in some cases it may be) it's not for lack of knowledge, but because we've seen how real world consumers are and use their heating systems. We can only adapt our installations when customers are ready to adapt to how they use them. I fitted a full heating system last week, all heat loss calculated, Rads sized adequately, set temps and flow temps perfectly, next week she's calling me up moaning her radiators aren't getting as hot as her old ones used to so she's decided to whack the boiler stat up full to 85c, despite my best efforts of going over it with her for an hour plus on how to get the most efficiency. There's nothing like customers, and they're always right as they say. But what can you do🤷♂️🤯
But combis are sized on Hot Water demand Simon, not CH! When sizing a Combi there’s several factors to consider, here’s some main ones; Incoming Mains Pressure & most importantly, Flow Rate!. Demand, unless there’s a house full of young kids needing Baths every day, HW demand from a Combi is minimal. With Cold fill Washing Machines & Dishwashers etc, stored HW is pointless. Showers; most big kids & adults shower, lower temperatures HW & a very efficient way of using HW. Combi boilers will be perfect in the majority of modern homes in the UK. I work New Builds & have never known one complaint about lack of HW. You know, we recently completed a 200 Plot estate & water flow rate was really poor, only 10Ltr/Min in most cases. We were fitting 35KW combis(not our spec), where, 24KW ones would’ve been big enough.
@@TheDickPuller did you even read what my argument was about 🤷♂️🤨 You've basically reiterated everything I pointed out. This video and other videos are based on the fact that most homes only need about 6-8kw for CH needs, and most engineers now days are massively oversizing this by installing 35kw plus combi's. I merely pointed out the fact that we have no choice because bigger boilers allow higher flow rates in situations where it's needed. Even combi's when on minimum CH mode are churning out 27kw depending on the boiler size, which according to these is massively oversized. To which I agree, but as you said, we buy combi's based on HW performance.
I think you need to clarify the on off measurement. As all the engineers that visited my us property strongly recommended leaving the house on most of the time to build up the thermal mass in the building Except on summer months as with weather temp difference sensors fitted most of that time it would just heat the hot water . Plus those that have typical open vent regular boilers the heat up time is significantly longer unless it’s an air to air design which normally is about the same and that smart controls with weather compensation are essential to get the most out your system . And why heat pumps aren’t really recommended for single occupant dwellings. Further to this lifestyle calculation has to be included. E.g .would a solar 8 pannel setup and Eddie connected to a system setup be better for those who mainly just use hot water and heat for a couple of hours morning and night
We’re looking at getting an ASHP, however we only have space for a 150L tank (3 bed semi, 2 adults 2 children) Will this be OK economically or would it be better for us to just get a combi boiler?!
I know this will be a very crude way of working it out, but if I know our gas usage through a cold period and can deduct our water/cooking use which I know from the summer, is that a reasonable way to estimate heat energy used to keep the house warm?
So if I had a measured 8kw property heat loss, what size heat kw pump would I look to buy? An 8kw to match the heat loss of the property or the next KW size up (say 12kw) to prevent being undersized?
as per the video they would say that if you have a smaller hot water storage then you'd want to oversize a bit to compensate, if you have a larger hot water storage then you are fine getting closer to your 8kw loss
I have a 5kw heat pump hybrid system and getting prices to add a cylinder and lose the boiler. Also extending downstairs. Installer has said the original unit is undersized and should be 9kw for existing floor plan and 12kw for new! It is and will remain a 3 bed semi… probably still less than 100 sq. Heat geek would recommend 3.5kw valliant for existing 85 sq floor plan so there is no way 12kw is right. Especially as valliant is 350% efficient whereas my existing LG can go over 400%. How can you rely on current skill base to do the heat calcs correctly??
Excellent videos! For the cheat sheet in this one showing W/m² loss for different property age insulation etc what's the presumed room temperature and outside ambient temperatures? Thanks.
@@HeatGeek And is that with 20º internal? Reason I ask is I've been quoted 93W/m² (matching your Victorian house example) but I have 400mm loft insulation, cavity wall insulation and modern double glazing but I have asked for 23º internal.
@@HeatGeek Thanks. I did think a a small % increase of Δt should only give the same % increased in W. I should try filling in the MCS spreadsheet myself to spot what's causing the excess loss.
We use gas for heating and hot water only. I'm changing from gas to heat pump so all that is needed is to look at the gas kWh used over a year to get the size of the heat pump.
Question about hot heater heating. If your target temp is 48 degrees what flow temp do you use? Do you target a dT like with the heating circuit? So you set the flow temp to increase slowly as the water in the tank heats, maintaining dT5-7? For a gas boiler is there much advantage to heating water using lower temps? The heat transfer is so good through a coil or heat exchanger that until the tank heats up to past 54 degrees you're going to have a condensing return temp, even at very high flow. Maybe this is too much for a YT comment :D
Any suggestions how to get heat pump quotes to be realistic about ASHP size? Have a property that's never used more than 71kWh of gas per day (smart meter, day in 2021 with 24 hour avg. temp. outside of -3.5oC) so ~2.8kW for space heat & water being quoted with 8-9kWh ASHPs. Your rough guide matches my combi usage (i.e. 30-50W/m^2 & 90m^2 floor area guide gives 2.7-4.5kWh). Aborting contract at design stage sounds ok in theory but with 10% deposit before to design is risky! When prompted, they blame overly cautious "MCS rules!" but won't give details.
Hi thanks for all your help, at the moment I have 7 type 21 radiators 2 type 11 in the home envelope and 2 towel 1 of which is large in the bathroom,+ 1 type 21 in the conservatory, the house heats my home with a 10 year old plus oil condensing combi boiler this heats my bungalow to a comfortable temperature in 30 minutes but I was surprised to find the flow temperature was only at 40 degrees i assume that the efficiency has decreased over the years so I think an ashp should work well on my 108sq meter bungalow what do you think thanks
Using the cheat sheet, comes up with a number in watts - 160m2 property * 30-50w/m2 = 4.8-8kW for our house. Elsewhere I've seen heat loss mentioned as kWh per day - is this the same thing? Or should I multiply that figure by 24?
The only 2 measurements used are kw. Then kwh per year. For kwh per annum multiply by 1500, but thats not howntou size the unit.. sizing the unit is the number you have already
@@HeatGeek is this because u values have changed surely as my bungalow was built in the 70s they would be accurate for this property or am I missing something
Or you could forget all the measuring, u values, etc and use my heat loss method which cost me nothing and tells me I need 6kW peak input to heat my house and on an average day just 2kW. With uk gas prices up 75%, perhaps electric heating, always the cinderela of home heating, may at last offer an alternative to gas. If my methodology is flawed, explain where I am going wrong.
Your method? What's that? Is it the method sometimes used where by you place a sensor inside and a sensor outside, input heat from a known heat source and measure the dt? If so we can't use that as we need a room by room for rad sizing
@@HeatGeek yes, correct, My video describes the method. It only works with direct electric heating. Don't you think it strange that with electricity costing 4 times per kwh as gas yet I estimate my next 12 months will cost £2050 including the latest 33% increase. That compares very favourably with the UK national dual fuel bill of £1950. So what is going on? Could it be the efficiency of gas fired systems overall is quite low? Boiler efficiency of 90% tells us little about the system efficiency as a whole. I think we live in interesting times when the monopoly of gas as the fuel of choice is being challenged and heat pumps is but one alternative. How will we be heating our homes in 10 years time? Now there's a question.
A proper engineer will always try and do heat loss calculations even if we have to do some guesstimating with regards to U-values of walls. @heatgeek can you please do a video about preheat margins?
Why is it not just measured? Any estimate is just going to be wrong depending on the amount of drafts you have and wind direction etc. If boiler efficiency measurement was mandatory (flow + temp measure) we would know how much energy is going into the property. That could then be logged over the year.
@@ChapmanPlumbing Yes but that seems to be on a loss calculation estimate from sizes of everything. Why not just measure heat loss by measuring the heat input? If it was logged, then at some point it would be equivalent to the assumptions made in the heat loss calculation, or you can account for outside temp easily, check night time to eliminate solar and so on.
@@zlmdragon. Thats a start, but really I'm thinking it should mandated on the boiler (at least as an option). We can also measure efficiency directly if we know the output.
Jesus there is no right answer for any of this that is rule of thumb. Every home in every area will be different. Windows, insulation, cracks and leaks all come into play. It’s an impossibly conversation to even have.
In-depthness - LOL, good video series. This hopefully will get super popular with rising energy prices and customers will start asking their installers the right questions.
A word of caution on the numbers on the cheat sheet. They are for a "typical" house (I assume two storey detached?). Different house "formats" can vary significantly as to the ratio of house "envelope" to floor space and this can greatly skew the numbers. For example, bungalows typically have significantly more exterior surface per square meter of floor space than two storey houses (I have an L shaped bungalow, and that has even more, with the two largest rooms each having 3 exterior walls). Mid-terrace houses can have a lot less effective envelope - the party walls really being more like internal walls than external walls. Semis/end-of-terraces are somewhere between detached and terraced. As is said, you can't miss out on the detailed heat loss calc for your home.
You might have told me this a few weeks ago before I measured EVERYTHING! Your cheat sheet is spot on :) presumably if I need 27kwh for heating then I'd need enough heat pumps that match that output? Eeek.
Love it , videos like this are a must for the end customers/homeowners, to start to understand what they are using / what they need to invest into reduce their heating bills, could just get the heating professional to fit better controls and commission their existing boiler and system to use as little heat/fuel as possible,
Ok, so here's my issue with these kind of topics, and please give me your input as I would be interested to hear your take on this point of view.
THE most popular boiler type in the UK is without doubt a condensing combination boiler, and for many reasons. The most popular being their versatility of not requiring stored hot water, for which a hell of a lot of homes in the UK benefit from this as space in most average 2-3 bedroom family homes is lacking.
Now here's my point, most smaller Combi's are around the 24kw range, which in your eyes is overkill for most UK homes in terms of heat loss, and I would agree. BUT, as I said, space is often very limited, so a cylinder and a lower KW S Boiler or Heat only boiler is out of the question. Then we have to factor in that 3 bed family homes may have as many as 6 people in that house, for which a good HW flow rate is needed. We can only get greater flow rates from larger combi's starting from about 33KW right through to 40+KW combi's. Otherwise we as installers get very dissatisfied customers that are constantly on the phone complaining that HW performance is terrible.
I've tried putting this point across on a couple of other channels and get accused of being a lazy installer that doesn't understand how to design systems, and this is not the case at all. You can go on most ex council estates in the UK and find either 1; there's no reasonable amount of space for a conventional/unvented installation 2; The customer doesn't want to pay the extra for that kind of installation or 3; just doesn't want a HW store period.
Sorry for the long post but it is a real issue real world installers face and more often than not, were backed against a wall.
Of course! If they can't have a tabk they can't have a heat pump.. we tell loads of customers they can't have them for many reasons.. we're saying they work where they work.. not "they work everywhere".. gas boilers don't work on the 20% of the country that's of grid. .
However the sunamp does get around this space issue very often as they're tiny.. and square...
Also. Most places have lofts
@@ChapmanPlumbing yes my main point was regarding boilers not ASHP. And in terms of fitting a cylinder in a loft, that's fine for smaller families with only maybe one child, but it doesn't last long when everyone is using it in a home with 2 or more children. You have to wait for it to heat up again after running a bath or when the wife or teenager take 20minute showers.
I'm not saying your points are wrong or anything like that, but nobody ever puts videos out discussing why so often heating engineers install larger boilers. It's not for laziness (although in some cases it may be) it's not for lack of knowledge, but because we've seen how real world consumers are and use their heating systems. We can only adapt our installations when customers are ready to adapt to how they use them.
I fitted a full heating system last week, all heat loss calculated, Rads sized adequately, set temps and flow temps perfectly, next week she's calling me up moaning her radiators aren't getting as hot as her old ones used to so she's decided to whack the boiler stat up full to 85c, despite my best efforts of going over it with her for an hour plus on how to get the most efficiency.
There's nothing like customers, and they're always right as they say. But what can you do🤷♂️🤯
But combis are sized on Hot Water demand Simon, not CH! When sizing a Combi there’s several factors to consider, here’s some main ones; Incoming Mains Pressure & most importantly, Flow Rate!. Demand, unless there’s a house full of young kids needing Baths every day, HW demand from a Combi is minimal.
With Cold fill Washing Machines & Dishwashers etc, stored HW is pointless. Showers; most big kids & adults shower, lower temperatures HW & a very efficient way of using HW.
Combi boilers will be perfect in the majority of modern homes in the UK. I work New Builds & have never known one complaint about lack of HW. You know, we recently completed a 200 Plot estate & water flow rate was really poor, only 10Ltr/Min in most cases. We were fitting 35KW combis(not our spec), where, 24KW ones would’ve been big enough.
@@TheDickPuller did you even read what my argument was about 🤷♂️🤨
You've basically reiterated everything I pointed out. This video and other videos are based on the fact that most homes only need about 6-8kw for CH needs, and most engineers now days are massively oversizing this by installing 35kw plus combi's. I merely pointed out the fact that we have no choice because bigger boilers allow higher flow rates in situations where it's needed. Even combi's when on minimum CH mode are churning out 27kw depending on the boiler size, which according to these is massively oversized. To which I agree, but as you said, we buy combi's based on HW performance.
I think you need to clarify the on off measurement. As all the engineers that visited my us property strongly recommended leaving the house on most of the time to build up the thermal mass in the building Except on summer months as with weather temp difference sensors fitted most of that time it would just heat the hot water . Plus those that have typical open vent regular boilers the heat up time is significantly longer unless it’s an air to air design which normally is about the same and that smart controls with weather compensation are essential to get the most out your system . And why heat pumps aren’t really recommended for single occupant dwellings. Further to this lifestyle calculation has to be included. E.g .would a solar 8 pannel setup and Eddie connected to a system setup be better for those who mainly just use hot water and heat for a couple of hours morning and night
Fantastic videos and its nice to have some fresh content in the industry
Thank you, this was very interesting and good solid information about heat loss.
We’re looking at getting an ASHP, however we only have space for a 150L tank (3 bed semi, 2 adults 2 children)
Will this be OK economically or would it be better for us to just get a combi boiler?!
I know this will be a very crude way of working it out, but if I know our gas usage through a cold period and can deduct our water/cooking use which I know from the summer, is that a reasonable way to estimate heat energy used to keep the house warm?
So if I had a measured 8kw property heat loss, what size heat kw pump would I look to buy? An 8kw to match the heat loss of the property or the next KW size up (say 12kw) to prevent being undersized?
as per the video they would say that if you have a smaller hot water storage then you'd want to oversize a bit to compensate, if you have a larger hot water storage then you are fine getting closer to your 8kw loss
Depends on available space for PV panels.
I have a 5kw heat pump hybrid system and getting prices to add a cylinder and lose the boiler. Also extending downstairs. Installer has said the original unit is undersized and should be 9kw for existing floor plan and 12kw for new! It is and will remain a 3 bed semi… probably still less than 100 sq. Heat geek would recommend 3.5kw valliant for existing 85 sq floor plan so there is no way 12kw is right. Especially as valliant is 350% efficient whereas my existing LG can go over 400%.
How can you rely on current skill base to do the heat calcs correctly??
Excellent videos! For the cheat sheet in this one showing W/m² loss for different property age insulation etc what's the presumed room temperature and outside ambient temperatures? Thanks.
-2/-3 ish... its only a ball park
@@HeatGeek And is that with 20º internal? Reason I ask is I've been quoted 93W/m² (matching your Victorian house example) but I have 400mm loft insulation, cavity wall insulation and modern double glazing but I have asked for 23º internal.
@@johnh9449 they're well out imo. You've got about 55w/m2 there. Ask to see their calcs/ hear loss report!!!!
@@HeatGeek Thanks. I did think a a small % increase of Δt should only give the same % increased in W. I should try filling in the MCS spreadsheet myself to spot what's causing the excess loss.
@@johnh9449 or pay heat engineer software for a 1 off use.. much better imo
We use gas for heating and hot water only. I'm changing from gas to heat pump so all that is needed is to look at the gas kWh used over a year to get the size of the heat pump.
Ir better yet use the heat geek heatvpu.p sizing cheat sheet. Slightly more accurate
Or further more, and imperative, do a heatvloss calculation. Your installer will do that though
Question about hot heater heating. If your target temp is 48 degrees what flow temp do you use? Do you target a dT like with the heating circuit? So you set the flow temp to increase slowly as the water in the tank heats, maintaining dT5-7?
For a gas boiler is there much advantage to heating water using lower temps? The heat transfer is so good through a coil or heat exchanger that until the tank heats up to past 54 degrees you're going to have a condensing return temp, even at very high flow.
Maybe this is too much for a YT comment :D
too much.. video on this exact subject due though and is covered in our course
I don't find this Excel sheet . A link is possible?
Do you pay VAT on a heat geek, heat loss calculation?
Yes. Or use our website for a free estimation
@@HeatGeek Thank you for replying so promptly. How do I go about getting a free estimation?
Any suggestions how to get heat pump quotes to be realistic about ASHP size? Have a property that's never used more than 71kWh of gas per day (smart meter, day in 2021 with 24 hour avg. temp. outside of -3.5oC) so ~2.8kW for space heat & water being quoted with 8-9kWh ASHPs. Your rough guide matches my combi usage (i.e. 30-50W/m^2 & 90m^2 floor area guide gives 2.7-4.5kWh). Aborting contract at design stage sounds ok in theory but with 10% deposit before to design is risky! When prompted, they blame overly cautious "MCS rules!" but won't give details.
I wouldn't worry. Pay the 10% deposit then see what there calcs are.. heat loss calcs are more accurate than my guide
Hi thanks for all your help, at the moment I have 7 type 21 radiators 2 type 11 in the home envelope and 2 towel 1 of which is large in the bathroom,+ 1 type 21 in the conservatory, the house heats my home with a 10 year old plus oil condensing combi boiler this heats my bungalow to a comfortable temperature in 30 minutes but I was surprised to find the flow temperature was only at 40 degrees i assume that the efficiency has decreased over the years so I think an ashp should work well on my 108sq meter bungalow what do you think thanks
it will work vry well, provided the flow temperature actually IS 40c! it may be broken/out of calibration or you may misunderstand the dial
The boiler has no temperature dial i checked the flow temperature with a true rms meter and a type k temperature sensor against the 22mm pipe
@@patregal great!
Hi heat geek what link is for the cheat sheet?
Please
Will post on Monday
@@HeatGeek thanks👍
Using the cheat sheet, comes up with a number in watts - 160m2 property * 30-50w/m2 = 4.8-8kW for our house. Elsewhere I've seen heat loss mentioned as kWh per day - is this the same thing? Or should I multiply that figure by 24?
The only 2 measurements used are kw. Then kwh per year. For kwh per annum multiply by 1500, but thats not howntou size the unit.. sizing the unit is the number you have already
@@HeatGeek Cool, thanks.
Do you use or teach to use a mears calculator to work out heat loss and are they usefull
Hi. No they are way too outdated.
@@HeatGeek is this because u values have changed surely as my bungalow was built in the 70s they would be accurate for this property or am I missing something
@@patregal your windows aren't 70s.. or loft insulation.. or draft proofing... but they were hugely oversized when back then..
Or you could forget all the measuring, u values, etc and use my heat loss method which cost me nothing and tells me I need 6kW peak input to heat my house and on an average day just 2kW. With uk gas prices up 75%, perhaps electric heating, always the cinderela of home heating, may at last offer an alternative to gas. If my methodology is flawed, explain where I am going wrong.
Your method? What's that?
Is it the method sometimes used where by you place a sensor inside and a sensor outside, input heat from a known heat source and measure the dt?
If so we can't use that as we need a room by room for rad sizing
@@HeatGeek yes, correct, My video describes the method. It only works with direct electric heating. Don't you think it strange that with electricity costing 4 times per kwh as gas yet I estimate my next 12 months will cost £2050 including the latest 33% increase. That compares very favourably with the UK national dual fuel bill of £1950. So what is going on? Could it be the efficiency of gas fired systems overall is quite low? Boiler efficiency of 90% tells us little about the system efficiency as a whole. I think we live in interesting times when the monopoly of gas as the fuel of choice is being challenged and heat pumps is but one alternative. How will we be heating our homes in 10 years time? Now there's a question.
You said something about a template to calculate heat losses ? No link in description .....
Description updated
Very useful thank you
A proper engineer will always try and do heat loss calculations even if we have to do some guesstimating with regards to U-values of walls.
@heatgeek can you please do a video about preheat margins?
Exactly
Why is it not just measured? Any estimate is just going to be wrong depending on the amount of drafts you have and wind direction etc. If boiler efficiency measurement was mandatory (flow + temp measure) we would know how much energy is going into the property. That could then be logged over the year.
as per the end of the end of the video there are a couple of options here
@@ChapmanPlumbing Yes but that seems to be on a loss calculation estimate from sizes of everything. Why not just measure heat loss by measuring the heat input? If it was logged, then at some point it would be equivalent to the assumptions made in the heat loss calculation, or you can account for outside temp easily, check night time to eliminate solar and so on.
@@zlmdragon. I did I couldn't find any. Most companies or heating system fitters are at best estimating heat loss using rules of thumb.
@@zlmdragon. Thats a start, but really I'm thinking it should mandated on the boiler (at least as an option). We can also measure efficiency directly if we know the output.
Thank you still non the wiser but will be a bit wiser cheers
Jesus there is no right answer for any of this that is rule of thumb. Every home in every area will be different. Windows, insulation, cracks and leaks all come into play. It’s an impossibly conversation to even have.
Correct, which is why the actual solution is a room hybriom heat loss and conversion factor
Square meterage? Lol! Don't you mean area?
Square meterage is area but defines the unit of measurement. Its a recognised term. Google it 👍