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Home warming thread (Read 8705 times)

Teaboy

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Home warming thread
February 08, 2022, 12:04:31 pm
I’ve not seen a similar thread but if there is one please point me in the direction.

I’m looking at the options for insulating and heating my house and becoming increasingly flummoxed by all the options so am hoping people here can help with the knowledge. Initial high level questions are:
1. Everything I read says you have to insulate and eliminate drafts but also says this can lead to condensation and damp problems. How do you get around this issue? Do you just have to keep the internal surface of walls warm enough so you don’t get condensation?
2. Does external thermal cladding really work? We have thick walls so by the time any heat reaches it we’ve already lost a load of energy to the walls? Is the idea, again, that you keep the walls at a consistent temp so you never actually lose the heat or is the theory that they work like a heat sink?
3. What thickness of internal wall insulation would make a noticeable difference?
4. Anyone got any stories to share about air source heat pumps in old houses? 

NaoB

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#1 Re: Home warming thread
February 08, 2022, 12:44:10 pm
Oooh, I'm really interested in this topic too. Our old boiler is on its last legs and we have been looking into the alternatives for replacement. Air source heat pumps are hailed as being more 'green' but seem to have a long list of drawbacks like high initial expense and not actually being that effective at heating water in cold weather. An electric boiler could be a good bet, at least more environmentally friendly than a gas version, but it would be helpful to hear if anyone has experience of installing / using one and how effective it is in practice. Although electricity still has a muddy footprint currently, no doubt this situation will continue to improve as more is invested into generating green energy going forward.

SamT

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#2 Re: Home warming thread
February 08, 2022, 12:46:45 pm
First up - Air Source on anything other than brand new, highly insulated dwellings will cost you an arm and a leg in electricity bills.

There is already quite a back lash growing, with lots of 'Angry from Kent' articles about how they've installed Air Source because they were sold a line by the installers about the Renewable Heat Incentive (RHI) payments earning them loads of money etc.  However, Electricity being about 4 times more expensive per unit than gas, coupled with the ASHP struggling flat out to heat their old homes means huge electricity bills.

There is soooooo much conjecture about insulating existing stone built walls.  In theory, insulating your home well is the sure fire way to save on fuel bills in the long run, but its just not that easy to do on existing and old properties.

If you do, breathable insulations like woodfibre should be looked at first.

Unless well installed, contiguous vapour control layers are installed behind your plasterboard, then interstitial condensation is a real risk.  This is condensation forming between the back of the insulation and the wall.  i.e. at the point that it suddenly gets cold.  This is why external insulation is often, technically a better way, but is much harder to get right as it completely alters the look and external character of you house.  (unless its already rendered).

This does create a high thermal mass dwelling, (thick stone walls as you suggest)  which is often considered to be a good thing.  i.e. once it gets up to temp, it offers a very steady state environment. So long as the heat is being prevented from escaping once its soaked through the walll, (see external insulation) little further heat is needed to keep it ticking over. 

Passiv Haus design is based (in part) in this concept.

Good ventilation is also needed.  Good extraction in showers and kitchens is essential along with provision of controllable supply of fresh air. (adequate trickle vents on windows, air bricks etc that can be shut in cold weather and opened up in mild weather.  (not that anyone does this much).

Its a flippin nightmare and our phone is ringing off the hook at work with folks bealing about their EPC ratings.

As a bit of wider education - please note - EPC ratings A-G are based on the expected fuel costs of the dwelling, not necessirly its 'efficiency'/green/eco credentials. (that word or at least its use, really triggers me).

So a straight move from cheap mains gas to expensive mains electricity, is going to take you say from a B rated EPC, to a C or D rated EPC.  Thus when the government say they want landlords to improve their homes to get C rated EPCs (currently E rated under the MEES regs) essentially, they are saying ditch the electric heaters and install mains gas combis.

Its all arse about face.

I digress.



SamT

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#3 Re: Home warming thread
February 08, 2022, 12:54:10 pm
Oooh, I'm really interested in this topic too. Our old boiler is on its last legs and we have been looking into the alternatives for replacement. Air source heat pumps are hailed as being more 'green' but seem to have a long list of drawbacks like high initial expense and not actually being that effective at heating water in cold weather. An electric boiler could be a good bet, at least more environmentally friendly than a gas version, but it would be helpful to hear if anyone has experience of installing / using one and how effective it is in practice. Although electricity still has a muddy footprint currently, no doubt this situation will continue to improve as more is invested into generating green energy going forward.

It all depends on your motives.

If you want to save money and lower your fuel bills, install new mains gas combi (while you still can).

If you want to help fight climate change, install an electric combi boiler, (might need electrics upgrade etc) and let the government worry about supplying a green grid.   However, your fuel bill will sky rocket.

If you have the capital, install solar PV panels to help reduce the electricity usage/fuel bill (and perhaps even a battery storage unit such as a tesla solar wall).

There is much talk of mains gas being replaced by Hydrogen.  All a nice idea, however I suspect we are a long long way off this.   You'll hear politicians talk about it, but not about where they're suddenly going to find all the hydrogen.

Teaboy

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#4 Re: Home warming thread
February 08, 2022, 01:05:34 pm
An electric boiler could be a good bet, at least more environmentally friendly than a gas version, but it would be helpful to hear if anyone has experience of installing / using one and how effective it is in practice.
If you think you plan to sell your house in the medium term you need to be wary that this will actually worsen your EPC rating, I was surprised to find this out recently as we now have contradictory govt policies!

Edit: Sam’s just covered this point better than me!
« Last Edit: February 08, 2022, 01:14:30 pm by Teaboy »

Teaboy

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#5 Re: Home warming thread
February 08, 2022, 01:17:21 pm
Thanks Sam, I’m still a bit unclear about how the condensation issue is typically considered an issue for old houses not modern, well insulated ones. Is it just that the internal walls never get cold enough for moisture to condense on them?

ali k

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#6 Re: Home warming thread
February 08, 2022, 02:03:17 pm
Thanks Sam, I’m still a bit unclear about how the condensation issue is typically considered an issue for old houses not modern, well insulated ones. Is it just that the internal walls never get cold enough for moisture to condense on them?

It can be an issue with modern construction methods if designed badly. This is why a condensation risk analysis is done.

The issue is the fact that old houses were never designed with insulation in mind so now with retrofit we’re trying to insulate around what is already there. And the ‘easiest’ way is often to put it internal to the cold structure which causes the issue Sam mentions. And in fact makes it worse because the internal insulation makes the walls even colder than they would have previously been if there was no insulation (=increased risk of interstitial condensation). Ideally it would always be external to the structure so you get no issues with cold bridging and the walls stay warm to avoid condensation. Basically it’s about where the insulation is in relation to the rest of the wall build-up.

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#7 Re: Home warming thread
February 08, 2022, 02:24:18 pm
I was under the impression that MVHR was the gold standard system for solving the condensation issue. But as nobody has mentioned it am I being beguiled by the marketing? Would love to instal MVHR on my victorian terrace but I could spend another 100 years trying to find all the cracks and draughts so I've resigned to save it for the next abode.

Interesting points on EPC I didn't know thanks.

SamT

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#8 Re: Home warming thread
February 08, 2022, 02:46:25 pm
MVHR is just a good extraction system.

If all the moisture content in the air is extracted, then there is nothing to condense out. 

MVHRs are very intrusive to retro fit into an existing dwelling.  You have to find routes for all your ducting to every room.  Nigh on impossible in a lot of dwellings.

They use quite a bit of energy to run (powerful electric fan running 24/7 to push the air around the ducting etc.)  Its been suggested that unless you've got a very air tight dwelling, i.e. an air leakage rate of less than 3 m3/m2/hr, they'll use more energy running than they'll recoup from the exhaust air.  That's fine if all you want to do is make sure you're extracting stale air and supplying fresh, but if you've got a leaky house then you're electricity bill will go up.

ali k

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#9 Re: Home warming thread
February 08, 2022, 03:03:06 pm
I wouldn’t install MVHR unless you get a blower door test on it first to know roughly how leaky it is.

Passivhaus Trust released a paper last year attempting to debunk what Sam says re: increased CO2 emissions in leaky houses if you install MVHR and advocating for them to be installed across the board but I think the jury is still out.

SamT

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#10 Re: Home warming thread
February 08, 2022, 03:17:10 pm
They're definitely great for ventilation and air quality and if that's your goal, fine.

However - without having the time to go and do some googling of specs and maths - i suspect they easily use more electricity per day than normal intermittent fans.

As to whether they recoup more than that in heat through reclaimed by the heat exchanger is probably incredibly hard to prove without a lot of experiments and research.

SamT

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#11 Re: Home warming thread
February 08, 2022, 03:39:25 pm
Must be on my 10th call at work today explaining how EPCs are based on price.

"But I've got super efficient (that word again) electric panel heaters!!!" Why is my EPC a D rating rant rant rant"

We need an automated message - "press one for an explanation of why you're disappointed with your EPC"

The next few months are going to be challenging.

SA Chris

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#12 Re: Home warming thread
February 08, 2022, 05:03:29 pm
Is there any easy way of figuring out where draughts enter the house, short of doing an air leakage test, which I know would fail so dismally as to be meaningless.

Our house definitely feels decidedly colder on windy days, could plug any obvious gaps with expanding foam if I knew where they were.

ali k

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#13 Re: Home warming thread
February 08, 2022, 05:57:21 pm
Is there any easy way of figuring out where draughts enter the house, short of doing an air leakage test, which I know would fail so dismally as to be meaningless.

Our house definitely feels decidedly colder on windy days, could plug any obvious gaps with expanding foam if I knew where they were.

Just pick a windy day in winter and go hunting! It really isn’t too difficult to identify the big ones. Use the back of your hand to feel the draughts or the smoke from an incense stick or something to see the smoke trail being blown about.

Most likely they’ll be around the loft hatch, lots behind kitchen units eg where waste goes through the wall (a pain to get to if not sealed at the time the kitchen was fitted though), between bottom of skirting boards and flooring/floorboards (pull carpets back and mastic seal), sometimes around boiler flue.

You’ll find them. Just depends how forensic you want to be and how much stuff you’re willing to disturb in an effort to get to them! Best done during refurb work so you don’t make a mess.

SA Chris

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#14 Re: Home warming thread
February 08, 2022, 09:59:38 pm
Thanks, incense stick is a good idea.

NaoB

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#15 Re: Home warming thread
February 08, 2022, 10:39:02 pm
Oooh, I'm really interested in this topic too. Our old boiler is on its last legs and we have been looking into the alternatives for replacement. Air source heat pumps are hailed as being more 'green' but seem to have a long list of drawbacks like high initial expense and not actually being that effective at heating water in cold weather. An electric boiler could be a good bet, at least more environmentally friendly than a gas version, but it would be helpful to hear if anyone has experience of installing / using one and how effective it is in practice. Although electricity still has a muddy footprint currently, no doubt this situation will continue to improve as more is invested into generating green energy going forward.

It all depends on your motives.

If you want to save money and lower your fuel bills, install new mains gas combi (while you still can).

If you want to help fight climate change, install an electric combi boiler, (might need electrics upgrade etc) and let the government worry about supplying a green grid.   However, your fuel bill will sky rocket.

If you have the capital, install solar PV panels to help reduce the electricity usage/fuel bill (and perhaps even a battery storage unit such as a tesla solar wall).

There is much talk of mains gas being replaced by Hydrogen.  All a nice idea, however I suspect we are a long long way off this.   You'll hear politicians talk about it, but not about where they're suddenly going to find all the hydrogen.

Thanks for the expert advice. Do you think gas will genuinely still be the cheaper option with all the recent (and future) price hikes?

My motive is to reduce my carbon footprint, but I don't have the luxury of being able to afford to do that by the sound of it. It's a shame that the greener alternatives for heating and transport have such high price tags attached, also seems like the technology and national infrastructure has some catching up to do before the majority of the population could consider switching.

Let's pretend I did decide to fork out for the higher running costs of an electric combi boiler - would it be as effective for generating hot water as a gas version?

SamT

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#16 Re: Home warming thread
February 09, 2022, 12:05:03 am
Thanks for the expert advice. Do you think gas will genuinely still be the cheaper option with all the recent (and future) price hikes?

Current price of gas - about 3.something pence per kWh
Current price of Electricity - about 17.something per kWh.

We still generate a lot of our electricity using natural gas.  10% at the moment, but this goes up on low wind days to 20% or more.
https://gridwatch.co.uk/

Gas price goes up, Electricity prices go up.

Sure, they reckon gas will get more expensive as it runs out.  But they've been saying that for over 10 years now, and I still see no sign of it.

Quote
My motive is to reduce my carbon footprint, but I don't have the luxury of being able to afford to do that by the sound of it. It's a shame that the greener alternatives for heating and transport have such high price tags attached, also seems like the technology and national infrastructure has some catching up to do before the majority of the population could consider switching.

I know, shit isn't it. We're all doomed etc etc etc.  ::)  :'(

Quote
Let's pretend I did decide to fork out for the higher running costs of an electric combi boiler - would it be as effective for generating hot water as a gas version?

I've not real world feed back as of yet.  Seeing a reasonable number of installations through work, but no feedback as yet.
Time will tell. 

Have a look at what's available here...

https://www.electric-heatingcompany.co.uk/electric-boilers/

Anything over 9kw (a good electric shower) is going to need some serious wiring/fuses.

12kW would need (I think, not a sparky) a 50Amp fuse and a 16mm cable which is pretty damned chunky. 

My electricity supply has just had been upgraded to a 100amp incoming fuse (due to electric car charging point installation) but that's for everything.  I have a feeling a 24 kW boiler would need 3 phase electricity supply which is going to cost potentially a lot of money and digging.  Any sparkys out there care to comment. ??

Once again the politicians flapping about, spewing buzz words, EVs, electric boilers, etc etc, without any thought to the real world implications.

Mind you - 10 years ago - there were practically no offshore windfarms and relatively few onshore wind farms.  Right now wind is providing 47% of the grids demand!!


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#17 Re: Home warming thread
February 09, 2022, 09:55:27 am
Modern gas combi boilers are ~ 96% efficient

Modern CCGTs (gas fired power stations) are at best 60% efficient

modern combi boilers are about as efficient a way to use gas as possible

ali k

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#18 Re: Home warming thread
February 09, 2022, 10:47:52 am
modern combi boilers are about as efficient a way to use gas as possible

Yeh. After a lot of deliberation and number crunching I can’t justify any alternative other than replacing our gas combi boiler when it gets changed this year unfortunately. And then spend the savings on insulation and other fabric improvements. At least it will be more efficient than the 10+ yr old one we have now.

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#19 Re: Home warming thread
February 09, 2022, 10:52:32 am
Reading this thread with interest after buying our dream house in November, just before all this energy price hike stuff kicked off.

For one, as a permanent WFH-er I try not to have the heating on when it's just me in the house, so have discovered the benefits of layering, quilted "shackets" and sitting with a down jacket over your legs!

As for the house, on the plus side, it has a nearly new combi boiler, and is modern construction (but not a new build) so is well insulated.

On the negative side - we have an Aga.

SA Chris

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#20 Re: Home warming thread
February 09, 2022, 11:04:14 am

On the negative side - we have an Aga.

Know so many people (ok maybe a few) who have moved in to a house with one, seen fuel bills after use, removed and sold.

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#21 Re: Home warming thread
February 09, 2022, 11:05:35 am
I haven't posted on here in years, Sam T has definitely outlined this beautifully.

I did my passivhaus contractors course last year at CSIC and they have a number of decent videos on the topic such as the following, specifically on retrofit.



Sorry I know I need to edit that to embed it, but it's been too long for me to remember how.

I've half ruined (slight exaggeration) my bungalow by carrying out various kind of insulation and vapour barriers over the years, by chipping away at insulating/air-sealing one room at a time, so currently only the loft conversion and around 50% of below the floor done, but not properly, since I used glass wool below the floor and above ceilings in the eaves, without a membrane to control prevent cold air blowing through solum and eaves from robbing the heat away. I only learned the futility of my actions on the course.

unless taken as a whole you do tend to create other issues or spunk your money away for no real gain (environmentally or otherwise), unless you're either very lucky (not like me) or well informed.



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#22 Re: Home warming thread
February 09, 2022, 11:18:02 am


For one, as a permanent WFH-er I try not to have the heating on when it's just me in the house, so have discovered the benefits of layering, quilted "shackets" and sitting with a down jacket over your legs!


North Face down slippers are absolutely incredible for this.

Our house is an 1890s terrace and draughty as fuck, not helped by having microbore heating pipes, single glazed windows (attractive, a big reason why we bought it) and a very small radiator in the front (north facing, coldest) room. That said, its been fine throughout this winter and the fuel bills so far are manageable, although obviously going to get more expensive.

With a house like this though, it seems to me that unless you're having major refurb work done (we aren't), the only way to insulate it efficiently would be to knock it down and start again!

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#23 Re: Home warming thread
February 09, 2022, 11:42:03 am


For one, as a permanent WFH-er I try not to have the heating on when it's just me in the house, so have discovered the benefits of layering, quilted "shackets" and sitting with a down jacket over your legs!


North Face down slippers are absolutely incredible for this.


I raise you an electric heated blanket!

It's not free, but is heavenly and  cheaper than putting the heating on.

SA Chris

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