Heating Design on 1880s Renovation

[Jeremy]

I'm renovating an 1880s Victorian semi-detached house. It's largely unmodernised, which means single-paned glass, damp cellar, damp walls, leaky chimney, vented hot water system with a cold water cistern in an overly large closet in the middle of a central first-floor room, unburied electrics etc. The upside is that it's a bit of a blank canvas and I'm looking forward to building up some self-building skills by doing a lot of the work myself. At this point I've browsed forums here and consulted with a few experts and have received some conflicting advice. I'm wondering if some experts on here with some simillar experience might be able to give my current plan a glance and poke holes as appropriate!

Images incuded here are hand-drawn (I work on a screen all day, so working with pencil and paper has been therapeautic) but drawn to scale. I've tried to annotate with some indications of underlying structure and heating I have planned. It's a reasonably big 5BR house, about 2k square feet in total, and rather drafty, with as-porous-as-one-might-expect solid 9" brick outer walls. There's also a cellar underneath half the sitting room (indicated on the diagram) with some dry rot in joists and sub-floor I'll be replacing after I can get it properly waterproofed. There's also some damp coming down from chimney in the first-floor room marked library, on which I'll get brickwork repaired and walls replastered. There's a 24kw Worcester boiler feeding 7 radiators. Half the first-floor has no heating at all and seems to have been largely unoccupied for the past several decades. I'm planning to remove gas stoves from the five fireplaces, remove the current 1980s layers, restore the fireplaces to their former glory and install wood-burning stoves in several of them. I'm aware there are differing opinions about stoves, but I'm pretty set on installing at least 2-3 of these. It's worth noting that sustainability is a key concern for us, so I'm not tied to the idea of offsetting costs invested in the heating system with energy bill savings 1:1. I do want to balance outlays across the different elements of the house, so can't dump £10k into an exotic hot water system or GSHP, but getting off fossil fuel inputs as much as possible is a key concern, thus my plans to install solar thermal or an ASHP eventually alongside use of biomass in the woodstoves.

My provisional plan for the (21x8') cellar is to excavate to get a flat floor (there's a good bit of rubble and the remnants of old brick flooring), put in a heavy membrane, 2" or so of sand and then a 4" wire-mesh reinforced concrete floor. I'll inject a damp-proof course into the walls, tank the whole thing, and to improve air flow put in a moisture extractor and probably also a humidifier to get moisture in there under control. I'll have zigbee / wifi humidity & temp sensors in all the rooms, so I will be able to monitor progress on this with some level of precision.

I'm thinking we'll remove the radiator from the kitchen, which is the "indoor" part of an extension which has a concrete pad installed, and replace with electric UFH on top of 50mm insulation boards. Above the extension on the first floor are two rooms without heating installed. There I'm thinking I'll install a few radiators.

Plan for bathroom upstairs is to completely gut and replace the bathroom upstairs, and install a thermostatic mixer shower and an electric towel heater style radiator.

One key question is how to drive the heating in this overall design. On one hand, it seems like the most efficient choice would be to put in an unvented hot water cylinder (250l) and have a plumber replace the hot water plumbing to be a 22mm pressurised system. I've seen good advice on here to get extra insulation installed and it seems like I'll probably get a Telford cylinder and get an extra 50mm of insulation added to minimise thermal loss. I'm also thinking I'll get a cylinder with connections for thermal solar as I will probably add solar PV and thermal water heating when we replace the slate roof in 3-5 years.

 

But I'm also wondering if it may be better to install a thermal store. They seem reasonable in cost, and also a bit easier to add in new inputs for heat. Ideally, I will add thermal solar and perhaps get boilers which feed in from the wood-burning stoves to store energy being generated while they are running. Hot water demand will be moderate - one bath a day for the kids and two showers for adults, which can be spaced out. There are five sinks in the house and the usual appliances. I don't need a million gallons per minute coming out of the shower, but do want to get away from the many years of combination boilers in the houses we've occupied which get cold every time someone turns on a sink.

 

In terms of insulation overall, I've got insulation in the ground floors as a mix of insulation boards in kitchen and sheeps wool (probably in the main rooms). I'll add a bunch of mineral or sheeps wool to the roof to get that up to 330mm. And we'll replace all the windows with proper double paned. I am also wondering if, since we'll be renovating all the walls and floors and the house will be unoccupied while I do initial work, if it would be worthwhile to install internal wall insulation. This seems to be a bit expensive, and time consuming. It seems like the green home grants aren't coming any time soon to Wales either. I'm resigned to the fact that it is unwise to convert a Victorian solid wall home to a passivehaus, but also wondering if this might, conversely, be a good way to get away from that "cold drafty house feeling". If anyone on here has done internal wall insulation as part of a renovation, I'd love to hear more about how it worked for you, especially in terms of wall dampness and overall warmth improvement.

 

Sorry for any rookie errors here - I'm still definitely learning how these systems all work together and thanks to anyone who has wisdom to share. I'm also happy to share photos of the house if that's useful.

[SteamyTea]

Welcome

 

Why bother with solar thermal?  It is a one trick pony, and once it has heated your domestic hot water, it will just sit there doing nothing, until it is time for a costly service.

PV is much better, and supplies energy in a more useful form.  How much can you get on your roof and is the roof at the correct angles to get full advantage of it?

 

Insulation is only part of the thermal losses, but as a rule, the more the better.  This is especially important if fitting any under floor heating, energy will leach away to the ground (so not that important on first floor, vital on ground floor.  Not talking about 50 or 70mm here , 200mm at a minimum.

The other big element of heat loss is ventilation.  Old houses are full of holes, so large, some small.  They all need to be fixed.  That is your hardest task by far.

 

Regarding wood burning stoves and sustainability.  They are just not, they churn out more CO₂/kWh that a gas boiler, and the particulates have no safe level, regardless of where you live.

Best avoided, and it makes blocking up the large holes that are chimneys easy.

 

As you currently have gas, you can calculate your current usage fairly easily.  This is useful as you can start to block up some holes and see what the improvements are.  Around windows and doors is a good place to start.

 

  

36 minutes ago, Jeremy said:

"cold drafty house feeling"

Just reread and noticed this.

Internal wall insulation is probably your only option, but you still need to make sure that there are no drafts behind it.  

 

You may want to rethink using wool.

 

Edited November 11, 2020 by SteamyTea

[Mr Punter]

What is the budget?

 

Insulation and airtightness/controlled ventilation will be key to better energy efficiency.

 

Would you look at external wall insulation?

[Jeremy]

 

Quote

Why bother with solar thermal?  It is a one trick pony, and once it has heated your domestic hot water, it will just sit there doing nothing, until it is time for a costly service.

PV is much better, and supplies energy in a more useful form.  How much can you get on your roof and is the roof at the correct angles to get full advantage of it?

 

 

Yeah, I expect you're right about this and after reading some other posts on here have already been starting to lean towards solar PV and simply using the electricity to heat water rather than solar thermal. Half of the (slate) roof is SW facing at about 30 degrees leaving about 56 m2 per half exposed to mount on solar panels. I'd aim to put on about 8kw worth of panels and this seems like a pretty good option, though I may hold out for a bit in hopes that the subsidies available on this improve somewhat as we seem to be in-between things just now on the public policy front. The house is also on a slope, near the top, and I have 0.7 acres of land behind it, so I'm also considering the merits of adding a small wind installation 2-5kw turbine which may actually be more efficient than solar PV. I need to test out the neighbours on this, and also do some work measuring wind, but generally it seems rather windy.

 

Quote

 

Insulation is only part of the thermal losses, but as a rule, the more the better.  This is especially important if fitting any under floor heating, energy will leach away to the ground (so not that important on first floor, vital on ground floor.  Not talking about 50 or 70mm here , 200mm at a minimum.

The other big element of heat loss is ventilation.  Old houses are full of holes, so large, some small.  They all need to be fixed.  That is your hardest task by far.

 

 

Another really good point, and I hadn't thought much about draught-proofing. Perhaps I felt defeated by the solid brick walls and regular air bricks around the house. I'd imagined I might get my hands on an IR thermal camera and see if I can go about plugging holes after new windows are in and waterproofing is installed (the whole house needs a damp-proof course as well). Any tips on the best materials to use on an old Victorian reno like this for plugging gaps?

 

I've been assuming that the kitchen is technically in a different thermal envelope (from what I can tell the wall in-between with the dining room on the other side is also a 9" solid brick wall) so was hoping that my plans to add electric UFH would address that part of the system. Do you really think I need more than 50mm on top of a cement foundation under the UFH coils and tile? For the remainder of the ground-floor 200mm was my plan for under-floor insulation. Since I'm rewiring the house and sanding floorboards, I'm planning on taking them all up, so this is a pretty uncontroversial step.

 

Ventilation is where I need some help especially. There are air bricks and open vents in several places around the house. I'm sure this was a great idea in 1890, but right now it's venting warm air straight out of the house which seems pretty foolish. I don't think an MVHR system is the right thing for this kind of (old) house, but am not sure what sort of tech will suit. Is there some intermediate step beyond a humidistat extractor fan?

 

Quote

Regarding wood burning stoves and sustainability.  They are just not, they churn out more CO₂/kWh that a gas boiler, and the particulates have no safe level, regardless of where you live.

Best avoided, and it makes blocking up the large holes that are chimneys easy.

 

As you currently have gas, you can calculate your current usage fairly easily.  This is useful as you can start to block up some holes and see what the improvements are.  Around windows and doors is a good place to start.

 

Re: wood burners, I take your point. They're not going to be as efficient as a condensing boiler. But what I have in mind for this installation is triple-burn stoves which are 80% + conversion efficient and produce no particulate emissions (that's the third burn). And I have at least some available timber supply that I can use for this as well. I'm pretty committed to avoiding fossil fuel extraction. That said, I'd be open to a gas-fired system in about 5-10 years when we have a sustainably produced domestic supply which seems increasingly likely, if a bit far off. I'll be running stainless-steel flues from wood burners out the chimneys, so it seems possible to have some level of draught proofing as I won't be doing open fires. There is an aesthetic value to wood fires which is hard to beat.

 

Quote

  

Just reread and noticed this.

Internal wall insulation is probably your only option, but you still need to make sure that there are no drafts behind it.  

 

Since the house is semi-terraced, I've ruled out external wall insulation and cladding as it would be pretty hard not to end up with a house that totally sticks out visually. I'm a bit anxious about the possibility of dampness behind internal wall insulation. Also this seems pretty expensive to install for the overall benefits. I might see what draught-proofing and waterproofing can do for me first and then add internal wall insulation if there are still some significant issues with heat escape.

 

Quote

You may want to rethink using wool.

 

 

I might be talked out of sheep's-wool, but I like the fact that it's supporting the local (Welsh) economy, has strong moisture/mold resistance and the fact that it's proper recycling and working with embodied carbon which doesn't involve fossil-fuel extraction.

Edited November 11, 2020 by Jeremy

[Jeremy]

57 minutes ago, Mr Punter said:

What is the budget?

 

Well, budget has to include (self-build) redo of kitchen, bathroom, and built-ins for several rooms, but on top of this I probably have £10-15k to put into heating system and insulation. Am also hoping to take advantage of available grants as the house pretty much ticks every box for these schemes.

 

57 minutes ago, Mr Punter said:

Insulation and airtightness/controlled ventilation will be key to better energy efficiency.

 

Yes - would love to hear more from experts about what sorts of draught-proofing I can do aside from fixing bricks/repointing and replastering. Are there good sealants that work with old solid brick wall construction? And esp. re controlled ventillation, I've admittedly been pretty unsuccessful at finding any useful options oriented towards renovation. I spent a lot of time getting up to speed on MVHR when we were thinking originally that we'd be doing new-self-build, but have shifted to a different sort of paradigm here.

 

57 minutes ago, Mr Punter said:

Would you look at external wall insulation?

 

Probably not. Would be hard to do this without totally alienating other properties on the terrace. Unless there are un-conventional options I haven't seen?

[SteamyTea]

4 minutes ago, Jeremy said:

doesn't involve fossil-fuel extraction

Many PUs are, as they now say, plant based.

Many Welsh sheep farmers drive inefficient vehicles.

 

Many people will tell you to use 'lime' on old buildings.  That is fine, as long as you are happy that your grandchildren are one ones to see it properly dry.

 

I am not sure about old buildings, renovation is a tricky thing.  But when they were built, one open fireplace was the norm, not central heating.

In a modern building, the moisture comes from the inside and condenses at the first place that the dew point temperature is conducive.  This is why vapour barriers are used.  The internal air is then mechanically vented out the building and the energy is recovered.

So a different solution to air bricks, which I think were to stop wooden joists rotting (and they failed anyway).

 

You can easily work out the heat losses though a material, thickness in m/W.m^-1.K^-1  you will soon see that you need a lot.

 

I would not bother with a thermal camera, just a candle will do to find the holes.

[Jeremy]

I'm interested in plant-based PU. Is there some more information on this out there?

 

LOL, re: lime. I agree. Not quite going to that level of conservation "purity". But do want to avoid internal moisture, so I'm aware that, without vapour barriers outside the insultation I may be creating my own new problems.

 

Great idea re: candle. But I might use a flashlight so I don't burn myself or light the house on fire. ?

 

Anyone have thoughts re: thermal store vs. UHWC for this system?

[A_L]

5 minutes ago, Jeremy said:

But do want to avoid internal moisture, so I'm aware that, without vapour barriers outside the insultation I may be creating my own new problems.

 

Vapour barriers go on the warm side of the insulation.

[SteamyTea]

26 minutes ago, A_L said:

Vapour barriers go on the warm side of the insulation.

Yes, and moisture permeable on the cold side.

It is how it works.

The detail is in choosing all the right materials.

39 minutes ago, Jeremy said:

interested in plant-based PU

Long time since I was using them. Used to be a company in the NE making the chemicals.

But think of it this way, if oil is turned to foam, it is not being burnt.

The trick is to get the overall CO2 emissions lower, not all components at the lowest.

 

[scottishjohn]

are you removing ALL the internal lathe+plaster -etc to get back to brick work ?

thats where your damp proofing system needs to be ,what ever you choose  + insulation is next thing in the wall build up 

how much reduction in room sizes can or will you accept ?

 

[Jeremy]

9 minutes ago, scottishjohn said:

are you removing ALL the internal lathe+plaster -etc to get back to brick work ?

thats where your damp proofing system needs to be ,what ever you choose  + insulation is next thing in the wall build up 

how much reduction in room sizes can or will you accept ?

 

 

This is certainly a possibility. All the walls need to be stripped and some of them have damage from rising damp so will need to have plaster completely removed. I'm already redoing all the floors also, so this is part of why I raised the question here, e.g. to gauge whether this might be worthwhile.

 

At an absolute minimum, I will have a damp-proof course installed by injection above the ground level on the outside walls. I'll have the floors up as well, so easy to put in insulation and add draught-proofing from below at the same time.

 

The rooms are reasonably big, so I don't mind losing 4-6" for vapour barrier and insulation if that will significantly improve livability of the house overall. Where it gets tricky is determining whether to do inside wall insulation and vapour barrier all the way around the outside of the house, including the portion which has been extended on the back - or pick specific rooms, especially the sitting room in front where we'll spend a lot of our time. And first floor rooms also? Is it an all-or-none sort of bargain?

[MarkyP]

2 hours ago, Jeremy said:

Re: wood burners, I take your point. They're not going to be as efficient as a condensing boiler. But what I have in mind for this installation is triple-burn stoves which are 80% + conversion efficient and produce no particulate emissions (that's the third burn). And I have at least some available timber supply that I can use for this as well. I'm pretty committed to avoiding fossil fuel extraction. That said, I'd be open to a gas-fired system in about 5-10 years when we have a sustainably produced domestic supply which seems increasingly likely, if a bit far off. I'll be running stainless-steel flues from wood burners out the chimneys, so it seems possible to have some level of draught proofing as I won't be doing open fires. There is an aesthetic value to wood fires which is hard to beat.

Do you have a link to an example of such a stove, would be interested to look into the testing standard. Most stove manufacturers are greenwashing their products like crazy with the gradual awakening of public awareness to the problems of smoke pollution. I'd be staggered if a stove could genuinely in normal use achieve zero fine or ultrafine particulate emissions through the highly variable usage that results from different size, types and moisture content of fuel, lighting up, refueling, air supply, poor flue draw and wind, de-ashing the pan, etc. Likewise the efficiency, will vary through a burn cycle and isnt very controllable, you typically generate far more heat than you need compared with other domestic heating systems which can be tuned and controlled. I do appreciate the aesthetic and pleasantness of the wood burner on a cold winter's day and am a relucant convert against stoves having previously been a fan. But I think they are a lifestyle choice rather than an eco one. Dont underestimate the interior air quality impacts during a burn cycle as well - very high levels of fine and ultra fine particulates emitted each time you open the door to re-fuel creating a warm polluted fug in your sitting room for the evening, you could not fit the stoves and take up smoking a couple of cigarettes in the evening instead. ?

 

*getsoffsoapbox*

 

Edited November 11, 2020 by MarkyP

[A_L]

5 minutes ago, Jeremy said:

and vapour barrier all the way around the outside of the house

 

See my previous comment. If what you actually want to do is keep liquid water penetrating the wall from the outside, the easiest way is an air gap (cavity) on the cold side of the insulation. There are other ways to do the same, e.g. renders which are vapour permeable but are liquid water resistant.

[SteamyTea]

14 minutes ago, Jeremy said:

Is it an all-or-none sort of bargain?

No, you can do both internal and external in different places. The only thing to be careful of is where they meet. A condensation risk assessment should be done for those parts. Not as hard as it sounds.

 

As it seems you are basically gutting the place, the one bit that is hard to do, the external wall between floors, becomes relatively easy.

Just make sure the joists are not going to be affected by the temperature difference, which is what affects the dew point.

Edited November 11, 2020 by SteamyTea

[scottishjohn]

the reason I asked the question if you were going bare brick things --you may look into spraying whole of inside of brick walls with closed cell spray foam --that  is impervious to moisture   If you make up studding inside bricks and then spray 30mm, minimum of foam to waterproof and seal studs --then add insulation between  them no reason why you cannot get modern insulation spec

- and no great loss in room size

 mount all floor joist on this frame work 

basically you build a TF house inside what you got now 

 worth  a consideration  if doing complete refurb?

Edited November 11, 2020 by scottishjohn

[Jeremy]

57 minutes ago, MarkyP said:

Do you have a link to an example of such a stove, would be interested to look into the testing standard. Most stove manufacturers are greenwashing their products like crazy with the gradual awakening of public awareness to the problems of smoke pollution. I'd be staggered if a stove could genuinely in normal use achieve zero fine or ultrafine particulate emissions through the highly variable usage that results from different size, types and moisture content of fuel, lighting up, refueling, air supply, poor flue draw and wind, de-ashing the pan, etc. Likewise the efficiency, will vary through a burn cycle and isnt very controllable, you typically generate far more heat than you need compared with other domestic heating systems which can be tuned and controlled. I do appreciate the aesthetic and pleasantness of the wood burner on a cold winter's day and am a relucant convert against stoves having previously been a fan. But I think they are a lifestyle choice rather than an eco one. Dont underestimate the interior air quality impacts during a burn cycle as well - very high levels of fine and ultra fine particulates emitted each time you open the door to re-fuel creating a warm polluted fug in your sitting room for the evening, you could not fit the stoves and take up smoking a couple of cigarettes in the evening instead. ?

 

*getsoffsoapbox*

 

 

Yes, I agree there is an aspect of lifestyle over eco, and lots of greenwashing about on this stuff. You can read a bit about the multiple burn approach here: https://www.stoveworlduk.co.uk/what-is-secondary-burn-on-a-wood-burning-stove. This is becoming increasingly relevant because DEFRA has, rightly I think, introduced new requirements for woodstoves, which are quite stringent. You can read more about the Ecodesign process, which is Europe wide, here: https://www.stovesonline.co.uk/ecodesign.html. I gather that one problem with the process is that not all small stovemakers can afford to go through the DEFRA process, so there will be some that you can get which aren't officially stamped but will meet that criteria. You can read another account (again, by someone committed to woodstoves to be fair) here:https://www.stovefitterswarehouse.co.uk/pages/are-wood-burning-stoves-to-be-banned.

 

In terms of thermal efficiency, it's really not hard to find or afford a stove with 80%+ thermal efficiency. The quality of fuel that you put into it will have some bearing on this, I gather, but there are stoves that are in the high 80s and even 90s in some cases. They are more expensive, but the technology exists. Burley is one UK manufacturer that sells stoves that are quite efficient: https://burley.co.uk/product/hollywell-9105-c-ecodesign-ready/

 

I don't know about inside air quality, but this is a concern I share. I'm in the process of building a PM1/PM2.5 sensor (another hobby) which I'll use to collect data and report back in some months once this is all in place in case people are interested.

[Jeremy]

1 hour ago, scottishjohn said:

the reason I asked the question if you were going bare brick things --you may look into spraying whole of inside of brick walls with closed cell spray foam --that  is impervious to moisture   If you make up studding inside bricks and then spray 30mm, minimum of foam to waterproof and seal studs --then add insulation between  them no reason why you cannot get modern insulation spec

- and no great loss in room size

 mount all floor joist on this frame work 

basically you build a TF house inside what you got now 

 worth  a consideration  if doing complete refurb?

 

Fab idea - will look into this! Any particular products you know of?

[scottishjohn]

35 minutes ago, Jeremy said:

 

Fab idea - will look into this! Any particular products you know of?

must be closed cell foam --not open cell -open cell is not water proof 

[joth]

48 minutes ago, Jeremy said:

 

Fab idea - will look into this! Any particular products you know of?

Bowtie use this technique on several of their retrofit projects you could have a browse through those.

 

In particular I know Kentish town EnerPhit was done this way (I was lucky to have a site tour just as it was on 2nd fix)

 

We have completed a total internal refurbishment to EnerPHit standard of this Semi-detached four bedroom Victorian house. The interior was completely stripped out leaving only the masonry exterior. A new load-bearding timber internal structure was constructed allowing the layout to be configured precisely to the client’s needs. The masonry envelope was then insulated with ICynene spray foam. This completely isolates the internal structure from the thermal envelope preventing thermal bridging from the heated interior to the outside. Moisture sensors have been installed between the brick and the insulation. Bow Tie Construction proposed this solution and we collaborated closely with the architects as part of the design process to develop an EnerPHit solution for masonry buildings that does not affect the external appearance and is cost-effective.

 

Edited November 11, 2020 by joth

[scottishjohn]

Just now, joth said:

Bowtie use this technique on several of their retrofit projects you could have a browse through those.

 

In particular I know Kentish town EnerPhit was (I was lucky to have a site tour just as it was on 2nd fix)

 

also getting quite popular in US for basement s --they spray the whole outside of anything below ground --very quick to do and also is very good air leak barrier--goesi nall the knocks and crannies by its nature 

[scottishjohn]

6 minutes ago, joth said:

ICynene spray foam.

beware there are 2 types --only closed cell is any good as a moisture barrier 

open cell is cheaper and good insulation --but not 100% moisture tight

Edited November 11, 2020 by scottishjohn

[SteamyTea]

Icynene is open cell.

 

http://www.uksprayfoam.co.uk/icynene-spray-foam-insulation/

 

There may be good reasons to not use closed cell in some places.

[scottishjohn]

3 minutes ago, SteamyTea said:

Icynene is open cell.

 

http://www.uksprayfoam.co.uk/icynene-spray-foam-insulation/

 

There may be good reasons to not use closed cell in some places.

they also make a closed cell -it you check the site you linked

[scottishjohn]

8 minutes ago, SteamyTea said:

There may be good reasons to not use closed cell in some places.

cost if moisture not a problem

closed cell is what they use for buoyancy  compartments in boats 

 https://uk.video.search.yahoo.com/search/video?fr=mcafee&p=matt+risinger+spray+foam+insulation+comparison#id=5&vid=c0e9d3091f607e0bb585cf3515a9a2b4&action=view

Edited November 11, 2020 by scottishjohn

[SteamyTea]

3 minutes ago, scottishjohn said:

they also make a closed cell -it you check the site you linked

What this one

http://www.uksprayfoam.co.uk/icynene-medium-density-foam-insulation/

 

Not used in the same situation.

 

All I am really saying is that the right product has to be used.