glpinxit's dumb questions- No 1 space requirement

[GLPinxit]

By way of introduction- we recently moved into a detached 2004-built 190 m^2 house in Somerset. It is currently heated by an elderly (alleged 83% efficient) oil-fired boiler nominally rated at 25KW and driving radiators and DHW. One of the early changes we want to make is to install an air-source heat pump (carbon-motivated choice rather than financial). The EPC rating was at D (68) but with our recommended recent changes (low energy lightbulbs) it would now be at C (69). The EPC assessed energy use for the house as heating/hot water 13750/2750 = 16500 kWh/year (this is difficult to validate as we haven't been here long and I'm using the bamboo-cane approach to assessing weekly oil consumption). 

 

I'm aiming for an MCS accredited installation but want to be an intelligent client so I'm going to ask some basic questions, here, and hope you lot can help me with the answers. It took us longer than expected to find the house and, while I'm far from knowledgeable, I've been using the time to pick up useful knowledge from this forum and others on BH. I'm a competent DIYer- including designing and installing gas central heating from scratch in a previous house and I'd quite like to do as much as possible myself (eg installing bigger radiators).  

 

Which brings me on to today's question: I'd like to manage Mrs glpinxit's expectations as far as possible and she'd like her beloved fridge freezer to be able to stay in the utility room- have I got enough space for this?

- once the old boiler goes there will be one consolidated space in the utility room 110cm wide by 235 high and 75 deep- at the moment I'm not clear if we will need to have a buffer, heat exchanger and sundry expansion vessels

- on the first floor a vast airing cupboard (with no plans to change it) currently houses the vented hot water cylinder which I anticipate will make way for something more 'suitable' (questions on this may follow)

- I need to redo the bathrooms and this is likely to mean I want to move the radiators so I'm working on the basis that the heat-exchanger will make this more straightforward. (Apart from anything else, we're on private drainage so I've no idea what I'd do with a load of antifreeze if I need to drain the system down from time to time.) Questions likely to follow on this too.

 

Thanks, in anticipation, for your time. 

[TW9]

If you want to minimise the stuff you have inside the house you could choose a monobloc heat pump. This has everything except the control box outside.

 

What bits and pieces you have inside will depend on your system designer. You're going to need pipework, pumps etc but if space is critical you could go for a pre-plumbed cylinder then it's all in the airing cupboard.

[ProDave]

Hi and welcome.

 

Changing the light bulbs will do nothing to reduce your heating bill and just shows what a stupid system the EPC is.

 

What you really need to know, is how much heat energy needs to be put into the building on the coldest winter day to maintain it's temperature. From that you work out the size of ASHP required and whether it is even practical or not.  A whole years oil consumption would allow you to make a reasonable assumption.

[Spreadsheetman]

Hi GLPinxit, size of the install is a tricky one. A lot of the pics of ASHP installs on the web look like they are in a boiler room of a ship rather than in a normal domestic house with limited space.

 

I'm in a similar situation to you, although my house purchase hasn't completed yet and my house to-be is only 145m2 built in 2001/2 (epc is a high D). Practically speaking, there is room for an exterior unit up to the permitted development 0.6m3 volume, the space where the floor-mounting oil boiler currently lives (about the size of a washing machine) and a compact airing cupboard where an unvented HW cyclinder lives. Any HP solution has to fit in that space and work with radiators (albeit larger if necessary).

 

I plan to live with the oil system for a winter while I do as much insulation as practical (loft, improved windows and doors, draftproofing) and work out the heat losses for all the rooms. At that point I'll have hopefully learnt enough and have enough data to be able to sense-check anything that HP installers say.

 

Maybe in a year's time they will have also fixed the EPC criteria which currently scores heat pumps like conventional inefficient electrical heating and could actually result in a worse rating after a more efficient system is installed.

[Marvin]

On 17/03/2022 at 13:00, ProDave said:

Changing the light bulbs will do nothing to reduce your heating bill and just shows what a stupid system the EPC is.

Sorry @ProDave I couldn't resist....  blame the boffins....

 

Yes and no.... changing your light bulbs from the old 100w ones to multiple LED ones will make your house cooler, and in winter your house will require more heat and in summer less cooling, but the heating effect is negligible.... but not the power usage to light the property.

[Spreadsheetman]

57 minutes ago, Marvin said:

Sorry @ProDave I couldn't resist....  blame the boffins....

 

Yes and no.... changing your light bulbs from the old 100w ones to multiple LED ones will make your house cooler, and in winter your house will require more heat and in summer less cooling, but the heating effect is negligible.... but not the power usage to light the property.

As I understand it the EPC (with all its faults) is meant to reflect total energy consumption, of which lighting is certainly a part. The house I am buying was marked down on its EPC (done 9 years ago) due to the large number of 50w halogen downlighters - now it will all be LED, so a big power saving.

[JamesPa]

1 hour ago, Spreadsheetman said:

As I understand it the EPC (with all its faults) is meant to reflect total energy consumption, of which lighting is certainly a part. The house I am buying was marked down on its EPC (done 9 years ago) due to the large number of 50w halogen downlighters - now it will all be LED, so a big power saving.

Both halogen and incandescent lamps are certainly much less efficient than LEDs at turning electrical energy into light.  However the electrical energy which is not turned into light is instead turned into heat and, during the heating season, this will offset the requirement to heat the house by other means.  Now for most people and for most houses, most lighting takes place at the same time as heating, and when this is the case all types of electric lighting are 100% efficient in turning electrical energy into either heat or light. 

 

There are obviously exceptions, a small proportion of domestic lighting takes place outside the heating season (summer and early autumn), and of course any lighting in areas which are unheated (garages, outdoors) is also an exception.  But its clear that the saving in total energy consumption in a typical domestic situation is nothing like as much as the difference in 'efficiency' would indicate.  I have never seen a calculation, but a rough guess might be that the reduction in energy consumption is somewhere around 20-30% of the figure that the crude calculations indicate (on the basis that roughly speaking houses tend to be heated from (say) mid September to mid April, but lights are probably on for about twice as much time in this period as during the summer period.  

 

In commercial premises, which are often lit throughout the year, the savings in energy consumption are greater, even more so where the accommodation is cooled in summer.

 

That' not to say that domestic LEDs aren't a good thing, they generally last much longer and there is definitely some energy saving, albeit nothing like as much as the simple calculation based on the comparison of the efficiency with which electrical energy is converted to light, would indicate.  If you have gas heating, then shifting the heating load from the 'lights' to the 'heating system' will reduce cost (because gas is cheaper than electricity, not because you are using less energy) and of course if you have ASHP then you also gain because a typical ASHP is 300% efficient at converting electrical energy to heat. 

 

EPCs reflect both the expected cost of energy and the expected energy consumption.  Depending on the heating type, the switch to LEDs will affect one much more than the other.  I have no idea whether EPCs are sufficiently sophisticated to make this distinction however!