Living in a passive house?

[Rubecula]

Hi, I introduced myself saying that I had some questions about living in a passive house.  Some of you thought the questions might be interesting.  I suppose what questions I have will depend on your answers to this first question.

What is your annual ennergy bill?

Based on our living here from last June to February Shell Energy has forcast an annual cost for electricity of £1900.  Our last house was a 1970's conventional brick structure where the combined gas and electricity bill was £1050.  Maybe I'm naive but I hoped the bill would be less not nearly twice a much!

Both houses are 4 bedrooms and there are only 2 of us since the kids moved out over 10 years ago.  Oh, and we have a tariff fixed until mid-2023.  Briefly, it's a highly insulated, triple glazed property, permeabilty 0.23, with air source heat pump, mechanical heat recovery and hot water heated by recovered air.

I guess you will need a lot of information about the house to provide us with some guidance but rather that overload you with the full house specification I'd first like to know if £1900 is what you would expect.  If you think it is then we'll just have to live with it.

Thanks,

Robin

[ToughButterCup]

16 minutes ago, Rubecula said:

...

What is your annual energy bill?

Based on our living here from last June to February Shell Energy has forcast an annual cost for electricity of £1900.  Our last house was a 1970's conventional brick structure where the combined gas and electricity bill was £1050.  Maybe I'm naive but I hoped the bill would be less not nearly twice a much!

...

 

Everyone is expecting a 40% price rise soon. So your bill in your old house would be around £1500. £1900 for your current house is a forecast only.  Forecasts are just that: an educated guess. They don't know (or rather I bet they don't know)  your new house is insulated to Passive House Standard do they?  

 

If you allow 1900/ 12 (just over £150 per month) initially and then allow things to settle down for a year?  You might be pleasantly surprised .

 

[ProDave]

What heated your previous house?  If it was not electricity then you would have paid your electricity bill plus a gas or oil bill?  what was the total.

 

ALL fuels has gone up a LOT, it rose sharply last October will rise another average of 54% at the end of this month and again in October probably.

 

We use about 1400kWh of electricity to heat the house with a heat pump each year.  BUT our total consumption of electricity is more like 6000kWh per year.  Heating cost is probably less than 1/4 of our usage.  I am trying to chip away and reduce the non heating usage but unless you never watch tv, never do any washing, don't use a fridge etc there is no solution.

 

And our bill would be bigger if it were not for the solar PV which we self use most of it.  I am experimenting with better ways to optimise that at the moment like only running the ASHP for the heating in the middle of the day. 

[MJNewton]

Be careful posing the question in terms of what other people's energy bills - in terms of £ cost - are like as we're all on different tariffs and energy types and it can become futile drawing any conclusions. Try and focus instead on energy usage - in terms of kWh - which you can then make much more meaningful comparisons between different house types, sizes, occupancy levels etc. You can still convert that into monetary values based on whatever options are available to you. I would also split out gas from electricity otherwise again you're going to get very misleading figures being bandied around, particularly given that your main area of interest is presumably heating costs (as that's all that I'd expect to differ in a Passivhaus to any other) and energy type can become really significant then given the difference in gas vs electricity costs.

 

For what it's worth, in our 125m² 2007-built gas-boiler heated developer box our average annual consumption is a fairly stable 8500kWH gas (~£400/yr at current rates) and 3500kWh electricity (~£740/yr). There are two adults home all day and a 4yr old, and we have a set temperature of 20C from 0700-2200. From what I gather from others here with highly efficient self-builds I'd expect our gas consumption to be just a fraction of this if we were in such a place, primarily to cover the base load of hot water heating which we seem to use <5kWh/day for judging by the summer gas consumption rates?

 

 

Edited March 23, 2022 by MJNewton

[Bitpipe]

57 minutes ago, Rubecula said:

Hi, I introduced myself saying that I had some questions about living in a passive house.  Some of you thought the questions might be interesting.  I suppose what questions I have will depend on your answers to this first question.

What is your annual ennergy bill?

Based on our living here from last June to February Shell Energy has forcast an annual cost for electricity of £1900.  Our last house was a 1970's conventional brick structure where the combined gas and electricity bill was £1050.  Maybe I'm naive but I hoped the bill would be less not nearly twice a much!

Both houses are 4 bedrooms and there are only 2 of us since the kids moved out over 10 years ago.  Oh, and we have a tariff fixed until mid-2023.  Briefly, it's a highly insulated, triple glazed property, permeabilty 0.23, with air source heat pump, mechanical heat recovery and hot water heated by recovered air.

I guess you will need a lot of information about the house to provide us with some guidance but rather that overload you with the full house specification I'd first like to know if £1900 is what you would expect.  If you think it is then we'll just have to live with it.

Thanks,

Robin

 

Two adults, two teenagers in a, just under, 400m2 passive house.

 

4KW PV on roof which brings in around £750 per year in FiT etc

 

Pre price hikes we were looking at under £4/ day on electric and under £2/day for gas averaged out over the year - so £6*365=£2190. Subtracting the FIT gives £1440.

 

Gas usage has not really changed since we moved in, about 12,000KWh per year but electricity usage is ticking up past 7,000 KWh as the kids get older.

 

Edited March 23, 2022 by Bitpipe

[AliG]

I keep reading people saying that they have changed to LED bulbs etc, insulated loft but bills have not fallen or gone up.

 

It seems that the average person has no idea how their energy bill is even calculated.

 

The right question would at least be how much energy do you use.

 

I have helped out a couple of people who have posted about their electricity bills on a Facebook utility forum. I was horrified that they were using as much or more electricity than we are. Indeed it made me wonder how much overall energy demand in the country could be reduced by explaining to people how to minimise bills.

 

Articles like this do not help in today's DM-

 

https://www.dailymail.co.uk/money/bills/article-10640385/Vampire-electrical-appliances-sucking-cash-bank-account.html

 

To suggest that not switching off phone chargers and leaving TVs on standby is a material proportion energy bills is nonsense.

 

A phone charger doesn't even register when not charging a phone. It might use 0.1-0.2 watts in this scenario, or 1-2kWh a year (40p)

 

TVs do not use the 4W quoted on standby, they would been breach of regulations. They use more like 0.5W. Maybe £1 a year, not the £10 quoted.

 

Some things are correct. Sky boxes use quite a lot of energy for example and amps are very inefficient users of power.

 

On the other hand a 3kW power shower used for 10 minutes a day would use 182kWh a year. Cut your shower time to 5 minutes (or don't turn it on for 5 minutes and do something else whilst it warms up) and save 91kWh. enough to run a phone charger for over 50 years.

 

Running you dishwasher on the eco mode instead of the fast mode might save 0.5kWh. So that could be 150kWh a year. It soon mounts up.

 

Like personal finance, maybe this is another thing to teach people at school.

[SteamyTea]

As many of you know, I am an extremely low user of energy (car not included).

Was sub 4,000 kWh last year.

My annual estimate came in from EDF, 3,600 kWh. Should be doable.

The only big differences I have are no TV (got 5 radios), no freezer, and I use a washing line.

[IanR]

2 hours ago, Rubecula said:

Based on our living here from last June to February Shell Energy has forcast an annual cost for electricity of £1900.

 

Hi Robin, welcome.

 

How does their forecasted kWh use match to what you actually used between June and Feb?  Have they just taken the total kWh you consumed, divided by the 8 months and multiplied by 12 to get a year's usage?

 

Even though that would be an over-estimate, since the 8 months usage includes 100% of the heating system, I suspect they've bumped it up a little higher, which is the typical model of the energy suppliers. There is a tendency now to have their customers financing their business, by always having them in credit.

 

The reality is that in a PassivHaus the heating season should now be over, and you likely haven't required space heating for the last few weeks. A PH house will only make a noticeable difference to the space heating proportion of you energy bill. Your hot water requirement, lights, cooking etc. will be pretty much the same as you old house if your lifestyle hasn't changed.

My energy bill is quite a bit higher than yours, but my non-space heating energy use is quite high.

Edited March 23, 2022 by IanR

[Rubecula]

Thanks all for your very helpful responses.  You've given me a lot to think about.  I'm going to be busy for the next couple of days but will come back to you when I've had time to digest all you have told me.

Many thanks,

Robin

[AliG]

Sorry, I realised I was ranting about the general questions I see re utility bills and not you specifically.

In your case I’d try and estimate the amount of energy you expect to use from historic bills and what you know of your build and see if their estimate is correct.

[TerryE]

@Rubecula, we have a passive-class house, but TBH reducing annual energy use wasn't our primary goal.  We made quite a few trade-offs between build costs, run-rates life style etc..  For example:

• A low energy house allowed to remove a lot of things that we would have needed in a classic build: we only have underfloor heating that was laid before the slab was poured and this is heated by a 3kW immersion heater. No complex central heating, no wall mounted radiators, no cold rooms, no cold ToD: everything in the house is the same temperature 24×7.
• The house has forced air circulation using MVHR so the air inside is always fresh.
• We could add ASHP since the UFH system was designed to allow adding ASHP, but to be honest we wouldn't get a net payback in maybe 7 years and especially given that ASHPs have a typical working life of 10 years.
• We also took the opportunity to make sure the outside was as near zero maintenance as possible, so we won't need to redecorate or do maintenance replacement in our remaining lifetime (we are 140 between us🤣). 

[Rubecula]

Thanks all for your input.  I understand that using the energy cost for comparison is not ideal.  In the mistaken belief that energy costs here would be less than our previous house I destroyed all our previous bills and so cannot compare Kwh consumption.  I think that we have got the system set up correctly but my objective in asking the original question was to see how energy consumption compared to similar properties.  I now see that there are probably too many variables to make a useful comparison.

TerryE, other than your use of an immersion heater in lieu of our ASHP the properties seem very similar in terms of construction and maintenance requirements.

For comparison our combined ages are 146!

[ToughButterCup]

On 23/03/2022 at 12:08, AliG said:

...

Like personal finance, maybe this is another thing to teach people at school.

 

I agree. With one caveat. Encourage Continuing engagement.

Anyone with GCSE maths has all the information necessary with which to 

• describe the problem
• gather the relevant data
• research how others have solved similar problems
• consider which method(s) to use to
• calculate the results and
• check them

and the same goes for GCSE Physics. 

 

The biggest problem is how the curriculum is taught - it still turns off so many people. 

 

Which is why I'm such a fan of Continuing Education.

For example: I can think of a few who still in middle age would benefit from a deeper understanding of ethics and the practice of ethical behaviour. 

Edited April 7, 2022 by ToughButterCup

[JohnMo]

I found through experiment that the lowest input (kWh) to the house for heating is batch charging the floor.  Basically the UFH goes on at 1.30am and is run until 7am with a flow temp of 30 deg.

 

Tried running the flow temp for the UFH as low as I could, continuously but the kWh input was huge (nearly double) in comparison.  For more or less the same temperature in the house.

 

On 23/03/2022 at 13:14, IanR said:

The reality is that in a PassivHaus the heating season should now be over, 

This depends where you live, ours went of, for a couple weeks and now had sub zero nights, little or no solar gain in the day and day time temps not much above 5 degs.  So heating is back on.

[jack]

36 minutes ago, JohnMo said:

I found through experiment that the lowest input (kWh) to the house for heating is batch charging the floor.  Basically the UFH goes on at 1.30am and is run until 7am with a flow temp of 30 deg.

 

Tried running the flow temp for the UFH as low as I could, continuously but the kWh input was huge (nearly double) in comparison.  For more or less the same temperature in the house.

 

Interesting you found this to be the case - I'm planning on trying this out next winter.

 

I'm on Octopus Go, and my peak rate electricity is about to go from 13.8p to nearly 30p per kWh in May. The off-peak rate is only going up from 5p to 7.5p, to there'll be an even bigger incentive to push things like heating into the four hour off-peak window.

 

I need to do some maths, but the modest reduction in COP caused by a slight increase in flow temperature will be swamped by the 4x cost difference between peak and off-peak rates.

 

The only question now is whether our 5 kW ASHP will be able to both heat our DHW and put enough energy into the slab during the four hour off-peak window during cold periods. I suppose we can just add a bit more if needed during the day.

[PeterW]

2 minutes ago, jack said:

The only question now is whether our 5 kW ASHP will be able to both heat our DHW and put enough energy into the slab during the four hour off-peak window

At the price differential you are quoting I would just be going for the first hour on the ASHP into the DHW and then switch to the immersion while the ASHP pushes heat into the slab. You can work out how much heat you need (from the losses and historical data  if you have it ) and alter the timing accordingly 

[JohnMo]

Difference in price between day and night is 4x.  So you could have cost saving with immersion on coldest days for DHW?

[jack]

1 minute ago, PeterW said:

At the price differential you are quoting I would just be going for the first hour on the ASHP into the DHW and then switch to the immersion while the ASHP pushes heat into the slab. You can work out how much heat you need (from the losses and historical data  if you have it ) and alter the timing accordingly 

 

Yes, a COP of 4 isn't very likely during that time of the year, so it's slightly cheaper to use the immersion off-peak than the ASHP during peak hours.

 

The main question will be controlling it all, and keeping it simple.

[jack]

2 minutes ago, JohnMo said:

Difference in price between day and night is 4x.  So you could have cost saving with immersion on coldest days for DHW?

 

Yup.

 

The question is whether I actually need to heat outside the off-peak period.

[PeterW]

1 minute ago, jack said:

The main question will be controlling it all, and keeping it simple.

Standard time switches ! My only niggle with them is that the thermostat is dumb so you always get heat at the beginning of the heat cycle not the end so you can end up needing additional heat during the day as the slab gives up heat in a fairly linear manner. 
 

I think @TerryE has an elegant way of doing it but it’s not off the shelf components so requires some technical knowledge. 

[JohnMo]

I'm just using wireless timer thermostat.

 

We like the house temp around 19 degrees.

 

I know if there is any sun out we will get solar gain also in the winter.  So I set the thermostat at 19.5 at 01.30 and at 18 at 07.00 this will switch off the heating, if it's not at 18.1 the heating will remain on for a while.  Have found the temperature continues to climb slowly until about 09.00 where it is at about 19 for the rest of the day.  Our living room is 20 at the moment (sun out), zero degrees last night, and 6 degrees outside now.  We are not quite passivhaus.

[Bramco]

On 23/03/2022 at 20:41, TerryE said:

We could add ASHP since the UFH system was designed to allow adding ASHP, but to be honest we wouldn't get a net payback in maybe 7 years and especially given that ASHPs have a typical working life of 10 years.

 

If you want to collect the £5k grant from the Boiler Upgrade Scheme you'll be on a lot longer than 7 years.

 

We're planning to run our system like yours, immersion heaters in the DHW tank and UFH system on Octopus Go at 7.5p/kWh for the four hours overnight and top up when needed.   But on reading that the Gov £5k scheme will now cover self builds, I asked around for some quotes for an ASHP installation.  It has to be MCS so you get on the renewables ripoff merry-go-round. 

 

You provide them all the details, professional heat loss analysis, the fact that the DHW UVC and UFH buffer tank are already installed. They come back with a daft price - latest was £14k for a 7kW Vaillant ASHP that you can buy on the internet for £3.75k.....  they'd estimated 72 hours for installation!!  Then they say they have to do a full heat loss analysis themselves and an EPC (the government website says specifically that it isn't needed  for self build.

 

I managed to get one company down to £8.3k but even then it's a ripoff.  Surely installing an ASHP is as labour intensive as installing a gas boiler.  Gas Safe is probably more onerous than MCS.  And a new gas boiler is about £2k of which say £750 is the boiler.

 

It's madness!!!  The double glazing and conservatory salesmen are making hay again...

 

Sorry - rant over.

 

PS If anyone knows an MCS accredited ASHP installer in the east midlands who won't take the p*** I'd love to get their contact details....

[jack]

2 hours ago, PeterW said:

Standard time switches ! My only niggle with them is that the thermostat is dumb so you always get heat at the beginning of the heat cycle not the end so you can end up needing additional heat during the day as the slab gives up heat in a fairly linear manner.

 

I'll probably get my HA system to control it, which perhaps counter-intuitively might make things simpler. Still requires some upfront thought.

[Adam2]

2 hours ago, Bramco said:

If anyone knows an MCS accredited ASHP installer in the east midlands who won't take the p*** I'd love to get their contact details..

I just had a CoolEnergy system installed (ASHP/UVC/Buffer). They did an inspection to sign off the MCS part. Was quite economical compared to the figures you're quoting. I know you don't need it all but they sell just the ASHP also.

[Bramco]

19 hours ago, Adam2 said:

I just had a CoolEnergy system installed (ASHP/UVC/Buffer). They did an inspection to sign off the MCS part. Was quite economical compared to the figures you're quoting. I know you don't need it all but they sell just the ASHP also.

 

Thanks for the reminder, I'd forgotten about them.   Did you get a regular plumber and electrician to do the install and then get them to do the MCS sign off?

 

Simon