Heat Pump EPC bad

akwexavante

I do use the words "MY GUT FEELING IS THAT".  It is conjecture!

The following is true and factful........

My own house was not adequately insulated when it's ASHP was installed as a heating system.

The ASHP struggled to maintain a satisfactory temperature and the electricity bill has higher than i was happy with.

I have now well insulated the building, i have upgraded pipework from 15mm to 22mm and insulated it well.

I have reduced drafts, i make sure i close all internal doors, especially the door at the bottom of the stairs.

I NOW HAVE A HAPPY WARM HOUSE and a CONSIDERABLY lower energy bill, i've slashed my heating bill by half by simply insulating, increasing pipe run size and reducing drafts and changing the way i live a little (Closing Internal doors).

NedS

Martyn1981 said:

ed110220 said:

Reed_Richards said:

The only property that does not "best suit" an ASHP is one that is so large and/or badly insulated that it is beyond the capacity of a single heat pump.  Heat pump ranges tend to have a maximum output of around 16 kW.  It's a myth that you need a well-insulated property for an ASHP but undeniably true that a poorly insulated property will be expensive to heat, whatever heat source you use.

For example, I replaced an oil boiler with a 12 kW ASHP.  The oil boiler cost me roughly £1000 per year to run at a time when the average cost of oil was around 50p per litre.  The price of oil is similar now so for someone paying £2000 or more per year for heating oil then it's likely they could not replace an oil boiler with a single heat pump.

Isn't the grain of truth in this myth that air to water heat pumps have a lower flow temperature and therefore heat the house more slowly, so need to run for longer and are best used to maintain a reasonably constant temp? If you compare that with blasting a poorly insulated home with heat say in the morning and then again after work, between which it gets cold, then the amount of heating (and heat loss) will be higher. It's not an apples to apples comparison but I can see why it would be made.

Yes I think what you are describing is possibly the 'reasonable' exception to what Reed Richards has explained, and to which I agree with him entirely.

I see this as more a 'type of use' issue. We are home all day, so our house is always occupied. I often wonder how an "always on" heat pump style of heating is going to suit those who are out at work for half of the day and are maybe used to turning the heating on for a 1 hour quick blast before they get up and again for a few hours in the evening when they get home from work before bed. Obviously a gas or oil boiler capable of chucking out huge amounts of heat is ideally suited to this task. I wonder how constantly heating the house all day (and night) when they are out or asleep would compare on running costs to their previous usage.

Martyn1981

NedS said:

Martyn1981 said:

ed110220 said:

Reed_Richards said:

The only property that does not "best suit" an ASHP is one that is so large and/or badly insulated that it is beyond the capacity of a single heat pump.  Heat pump ranges tend to have a maximum output of around 16 kW.  It's a myth that you need a well-insulated property for an ASHP but undeniably true that a poorly insulated property will be expensive to heat, whatever heat source you use.

For example, I replaced an oil boiler with a 12 kW ASHP.  The oil boiler cost me roughly £1000 per year to run at a time when the average cost of oil was around 50p per litre.  The price of oil is similar now so for someone paying £2000 or more per year for heating oil then it's likely they could not replace an oil boiler with a single heat pump.

Isn't the grain of truth in this myth that air to water heat pumps have a lower flow temperature and therefore heat the house more slowly, so need to run for longer and are best used to maintain a reasonably constant temp? If you compare that with blasting a poorly insulated home with heat say in the morning and then again after work, between which it gets cold, then the amount of heating (and heat loss) will be higher. It's not an apples to apples comparison but I can see why it would be made.

Yes I think what you are describing is possibly the 'reasonable' exception to what Reed Richards has explained, and to which I agree with him entirely.

I see this as more a 'type of use' issue. We are home all day, so our house is always occupied. I often wonder how an "always on" heat pump style of heating is going to suit those who are out at work for half of the day and are maybe used to turning the heating on for a 1 hour quick blast before they get up and again for a few hours in the evening when they get home from work before bed. Obviously a gas or oil boiler capable of chucking out huge amounts of heat is ideally suited to this task. I wonder how constantly heating the house all day (and night) when they are out or asleep would compare on running costs to their previous usage.

Yes it's definitely a real and fair scenario, unlike many of the criticisms of HP's.

Would a HTHP work in that situation, I don't know enough?

NedS

Martyn1981 said:

NedS said:

I see this as more a 'type of use' issue. We are home all day, so our house is always occupied. I often wonder how an "always on" heat pump style of heating is going to suit those who are out at work for half of the day and are maybe used to turning the heating on for a 1 hour quick blast before they get up and again for a few hours in the evening when they get home from work before bed. Obviously a gas or oil boiler capable of chucking out huge amounts of heat is ideally suited to this task. I wonder how constantly heating the house all day (and night) when they are out or asleep would compare on running costs to their previous usage.

Yes it's definitely a real and fair scenario, unlike many of the criticisms of HP's.

Would a HTHP work in that situation, I don't know enough?

Ultimately it's going to depend on the output rating of the device. When we moved into our property a few decades ago, there was a large capacity oil boiler (not sure how big exactly). We'd turn the heating off or right back overnight on the thermostat, and get up to a cold house. We'd turn the heating on, and 15 mins later the rads would be hot. 10 Years later we had a new oil boiler which was obviously of lower capacity (who knew about output capacity in those days), and the most noticeable difference was it now took 30mins before those rads felt piping hot.

A heat pump can only put out it's rated output. Even a HT heat pump can only put out it's rated output, albeit at maybe higher flow temps, so it's going to take a 16kW heat pump longer to heat those rads to 60C than it would take a 24kW gas or oil boiler. Once that flow temp is achieved, then all that is required is an output capable of matching the rate at which the emitters (rads) can dissipate the heat and/or the heat loss of the property. So it's the speed or time taken to warm the house from cold to an acceptable temp that we are considering (and the perception that the radiators feel hot so the heating must be doing something), and I don't think a HT heat pump will make a significant difference in that respect. Ultimately, any heating system is also limited by the size (and hence output) of the emitters, so if the rads are the limiting factor, installing a 48kW gas boiler isn't going to heat the house any quicker if the maximum output of the emitters is limited to 18kW at 60C flow temps.

The problem HT heat pumps 'solve' is being able to put out sufficient heat with small/undersized radiators. If radiators are (under)sized such that a flow temp of 60-70C is required to emit sufficient heat to keep the property warm, then a regular heat pump isn't going to be able to achieve those flow temps. The best solution would be to replace the emitters with larger ones so the system can run at efficient 35C flow temps, but that may require significant work so it's easier for installers to fit a HT heat pump onto the existing heating system, but that is not a solution I would ever want as running costs will be significantly higher.

FreeBear

NedS said:

Reed_Richards said:

The only property that does not "best suit" an ASHP is one that is so large and/or badly insulated that it is beyond the capacity of a single heat pump.  Heat pump ranges tend to have a maximum output of around 16 kW.  It's a myth that you need a well-insulated property for an ASHP but undeniably true that a poorly insulated property will be expensive to heat, whatever heat source you use.

I could not agree more. It infuriates me immensely when I hear Grant Shapps (and others) say his 3 bed semi isn't suitable for a heat pump. There is nothing special about a heat pump - it's just a heat source like any other heat source (gas or oil boiler) bolted on the end of a heating system that produces heat.

I have a late 1920s semi here. Spent a bit of money replacing doors & windows and increasing insulation*, along with plugging all the cold draughts. Although I'm still heating with gas, 4-6kW is plenty to get the temperature up to a comfortable level with a 45-50°C flow temperature. Well within the capabilities of a heat pump.

*) Some of the walls have been insulated internally, and I've not measured any real change in the rate of heat loss or a reduction in energy consumption. I'm not entirely convinced that it is worth the expense of doing the remaining walls.. Loft insulation is cheap, and increasing levels from 200mm to 300mm (and more in places) has been worthwhile.

Martyn1981

Thanks Ned, great explanation, makes total sense now you've explained it.

Reed_Richards

 I am pleased to see that my comment sparked some debate.

One further observation; if you get a heat pump installed to MCS standards then a detailed evaluation of the heat loss of your house will be made first, and your heat pump and radiators will be sized to meet the needs of your house.  So what happened to @akwexavante should not happen to you.  I think that to qualify for the £7.5k subsidy you are obliged to get the installation done to MCS standards.  But if you have a heat pump installed "free" under the ECO4 scheme (or similar) then I don't think that the same obligation applies.  And if you buy a new house with a heat pump pre-installed, make sure you see its MCS certificate.        

NedS

Reed_Richards said:

 I am pleased to see that my comment sparked some debate.

One further observation; if you get a heat pump installed to MCS standards then a detailed evaluation of the heat loss of your house will be made first, and your heat pump and radiators will be sized to meet the needs of your house.  So what happened to @akwexavante should not happen to you.  I think that to qualify for the £7.5k subsidy you are obliged to get the installation done to MCS standards.  But if you have a heat pump installed "free" under the ECO4 scheme (or similar) then I don't think that the same obligation applies.  And if you buy a new house with a heat pump pre-installed, make sure you see its MCS certificate.        

Mine was installed under the ECO4 scheme, and we certainly had a full room by room heat loss survey conducted and the system was designed with radiators sized to the heat loss of each room, as well as the overall whole house heat loss. We have an MCS certificate for the installation. I'm not sure if it's a requirement, but as it's government funded, I suspect it is.

Like you say, if the very first step of the process does not involve a full room by room heat loss survey then I'd be concerned. Expect a guy with tape measure to measure every room together with the size of all doors and windows, and existing radiators (takes 1-2 hours depending on size of the property). Without that as a starting point, it is simply not possible to design an ASHP system effectively.

michaels

We had an EPC done under the new rules and got marked down for lighting.  We probably have 50 plus bulbs but one was a cfl from when a led had failed and we didn't have a suitable replacement on hand and another had no bulb for the same reason.  Less than 100% led you get marked down which I guess is fair enough but you then get the 'switch to all lex and you could save £100 a year' advice.... Lol