New member - stuck for what to do next to warm the house

[Sparrowhawk]

Hi everyone,

 

5+ year reader and finally taken the plunge to join.

 

It's almost 3 years since we bought our house, a 1920's detached house extended twice (late 1990s/early 2000s, the latter extension considerably better quality than the first). I wanted to build a Passivhaus but the impossibility of finding a plot at a sensible price prevented that.

 

We soon discovered this house was cold and draughty and we could see daylight in the eaves storage. Since then I've sealed all the obvious drafts, used a thermal camera to try and find others, had the 3 worst windows replaced with triple glazing (an expensive mistake: I thought it would fix these rooms as the windows weren't airtight but it didn't), but it's still a cold house. Living here during the cold spell that's just ending drove me to join this forum as I'm not sure what to do next.

 

We need a new heating system (25yr old boiler, radiators of same age) which I'm expecting will make the house warmer but won't reduce our gas usage unless I can reduce heat loss.

 

Looking forward to getting stuck in!

[ToughButterCup]

Welcome: birdwatcher by any chance?

 

Anyway, after a five year 'lurk', whadya think of the place?  Useful innit? Trouble is there's too much information here - lots of wading to be done without any immediate (stress immediate) return on useful information. But, with five years worth of looking around you'll be aware of the inherent complexity. So - keep it simple - to start with anyway.

 

The shorter the question - the better. The more images, the easier it is for us to help you. A video will help (see  Accepted file types below).

 

Dunno about you, but I hear more sparrow hawks than I see....

[Sparrowhawk]

Just now, ToughButterCup said:

Welcome: birdwatcher by any chance?

 

Yes, keen very amateur birdwatcher and enjoying the coastal waders and occasional marsh harrier down here. Are you?

 

Just now, ToughButterCup said:

Anyway, after a five year 'lurk', whadya think of the place?  Useful innit?

 

I have found Jeremy's threads invaluable, as well as people's assessments of products e.g. Sunamp when thinking "could that be better than replacing our tank like-for-like. It's also appears to be a less... intimidating forum than some of the others with better natured members and fewer spats and general aggro. We shall see if that holds true 😁

 

Just now, ToughButterCup said:

Trouble is there's too much information here - lots of wading to be done without any immediate (stress immediate) return on useful information. But, with five years worth of looking around you'll be aware of the inherent complexity. So - keep it simple - to start with anyway.

 

The shorter the question - the better. The more images, the easier it is for us to help you. A video will help (see  Accepted file types below).

 

Great advice. I shall try and break down the "WTF do I do next?" into intellible bite-sized questions. Always the hardest part with a mind teeming with ideas and aware of the dependencies that "if I start to do this it'll impact this that and the other bit, which means I then need to do that as well and I think I'll have a nice sit down instead and pretend it's warm".

 

Just now, ToughButterCup said:

Dunno about you, but I hear more sparrow hawks than I see....

I don't think I know what they sound like! We have a local pair and before we started taming the wilderness that was the garden the female used to bring pigeons and eat them under our bushes. On the second day of this cold spell the male snatched a bird off the bird feeder and I've spotted him hanging around on neighbours' roofs keeping an eye out for more snacks.

[MikeSharp01]

22 minutes ago, Sparrowhawk said:

 

We need a new heating system (25yr old boiler, radiators of same age) which I'm expecting will make the house warmer but won't reduce our gas usage unless I can reduce heat loss.

It will as you will get a much more efficient boiler today - we did the sums here and came down to a modern 27kW boiler from a 32kW 30 year old one and still we use a lot less gas than before.

[Sparrowhawk]

10 minutes ago, MikeSharp01 said:

It will as you will get a much more efficient boiler today - we did the sums here and came down to a modern 27kW boiler from a 32kW 30 year old one and still we use a lot less gas than before.

Thanks Mike that's awesome to hear. No heating engineer I've spoken with has said more than a handwavy "it should save you money" yet.

 

Currently doing my radiator sizing calculations. delta-t 35 will not cut it for the coldest periods, but looks like it'll work nicely the rest of the time.

[JohnMo]

As said new boiler will be leaps an bounds better as far as kWh used.  If you are replacing consider the rest of the system at the same time.  A 25 year old system will be full of debris from corrosion etc.  You may be better do a full re-plump or at least a power flush, then while you are at make sure the rads can heat your house at a low flow temps circa 30-40 degs. That will make the house heat pump ready, and you will benefit with even better boiler efficiency.

 

You need a boiler that has two different flow regimes, one for hot water, the other for central heating, most can do this. But gets plumbed and wired slightly differently.

 

Not sure doing a delta of 30 on radiators makes much sense.  Most modern boilers will manage the delta T, by modulation of pump output at high flow temps mine will give a delta T of 20, at low temps a delta T of 4.

[Marvin]

Hi @Sparrowhawk

 

The below is my overview.  Whilst I know you are going for a new boiler, the process below would still be the same. You will save a lot more over time fixing airtightness, the insulation and installing mechanical ventilation. Triple glazing is the most expensive element to install per m2 with the least energy saving(although important when everything else is high spec).

 

 

Get yourself a heat loss calculator ( I use an excel spreadsheet for this ) and play with the elements and you can work out what gives you the best money spent/ money paid. 

 

Normal double glazing with a U-value of 1.2 versus your triple glazing say high spec 0.6 U-Value. Inside temp 20 centigrade, outside temp zero C will give  a saving of about 10.6Watts per square meter. (ignoring any non air tight issues with the old double glazing window installation or the rest of the building) 

 

 

 

Aim to go APE 

It worth considering all the AIM and APE elements before making decisions. That is Airtightness, Insulation, Mechanical Ventilation with Heat Recovery OR Heat pump Ventilation, and Air Source Heat Pump, Photovoltaics and Electric Vehicle.

 

Some of these will not work properly without the others, and some will complement others:

 

1. A MVHR will not work properly without Airtightness.
2. An Air Source Heat Pump will have to compensate for the lack of Airtightness and/or Insulation to the degree that the benefits become questionable, especially during winter, without them.
3. An ASHP uses electricity and Photovoltaics can supply a little during winter and a lot during summer when cooling can be a problem and an ASHP can supply cooling.
4. PV can supply a little to an Electric Vehicle during winter and plenty during summer if your vehicle is at home during sunny days.
5. Extending a property and only doing AIM works to the extension will be no good, you have to do all the property within the thermal envelope. 

 

And thinking of running costs:

a)     Airtightness and Insulation should have no running costs and last (Well, loft insulation lasts over 40 years, in our experience) with the exception of UPVC  units for windows and doors, but that being said it will last 30 years?

 

b)    Our MVHR unit servicing 100m2 floor sized home uses about 260kWh a year; far far less than would be used to heat incoming cold fresh air in winter, and we clean the filters twice a year.

 

c)     ASHPs are, in my opinion, still in their infancy but we are now in the second year of use here. We were very careful to follow best practice in the design and installation of our system, did a lot of bespoke tweaking, and we now have an upgraded 1970’s timber framed bungalow that uses less than 25kWh per year per m2 of floor for heating.

 

d)    PV would be a lot less attractive if there is no ASHP or EV (or battery backup) or diverter to the hot water immersion. In my humble opinion, if you have a suitable roof you should install as much a physically possible. Electricity production costs (cost per kWh) are difficult to evaluate because it depends how much is used and how much is supplied to the grid. We decided to go with the PV cost divided by 7 years, which for us works out at £1.60ish per day. Yesterday the PV produced 12kWh all of which we used. Remember, 5kW of PV panels will not produce 5kW because you would have to have:

                         i.         No shadowing of any of the panels during sunlight hours (like trees, buildings or chimneys.

                       ii.         All the solar panels face exactly the right angle in relation to the summer solstice midday sun for their                                           position on the planet. (Perfect angle facing south and perfect slope)

                      iii.         solar panels completely clean

                      iv.         the sun is completely unobscured

                       v.         the Inverter is 100% efficient

                      vi.         all the other losses due to cables, and equipment, and so on.

 

e)    Knowing the above PV limitations professional installers often add extra panels to make up for these losses. (Our inverter allows us to add roughly 28% more panels than its kW rating)

f)      PV panel installations will produce about one fifth of the power in the winter compared with what is produced in the height of summer.

 

g)    The electric vehicle and charging from the PV only really works if you can have the vehicle plugged in during the day and supply over 3kW from your PV (or a large proportion of that). This is why we went for the biggest PV that would fit on the roof.  We then installed a system which only charges the when the PV is on and generating over 2kW in winter and 3kW in summer. (we have a 13amp charging system).

 

So, if finances cause you to have to consider only a few in my humble opinion AIM first and go APE later. (But prepare the property for the APE works as much as you can).

 

Best of Luck

 

Marvin

[ProDave]

I spent the first 25 years of my life in the 1930's family home, then later I went and bought one myself.

 

My overriding memories of both, are being cold, even when pumping a massive amount of heat in, and high heating bills 20 years ago when energy was "cheap"  I would not want to be owning or heating one now.

 

IMHO they need some serious updating.  Ours was all solid walls that would need internal or external wall insulation, and the floors were partly solid and partly suspended timber, both would need lifting and insulating properly.  The timber ones would be easiest but the solid floor part would be a lot of digging up, digging down and building up again with proper insulation.

 

I would only buy another if it was sold at a "project" price, which sadly does not seem to be the case even now.

[Spreadsheetman]

My condolences. I lived in a 1930s semi with solid walls for many years and the only saving grace was the living rooms and (used) bedrooms were on the party wall so inherently warmer. Really doing anything serious about the heat losses would have been so expensive and disruptive that I just couldn’t bear to do it.

 

Have you done a room-by-room heat loss analysis of the property?

[ToughButterCup]

2 hours ago, Sparrowhawk said:

...

I don't think I know what they sound like! 

...

 

Here you are .....

 

They have a very much more interesting call  when they miss a strike. You can hear the irritation in it. It's based on the one in this video, but is much harsher , repeated quickly and more 'p!ssed_off'

[Sparrowhawk]

2 minutes ago, Spreadsheetman said:

My condolences. I lived in a 1930s semi with solid walls for many years and the only saving grace was the living rooms and (used) bedrooms were on the party wall so inherently warmer. Really doing anything serious about the heat losses would have been so expensive and disruptive that I just couldn’t bear to do it.

 

That is my fear that it is uneconomical to do anything about it. We have a cavity (filled with electrical cables) and all air bricks vent the cavity so in effect we have single-block-width solid walls around our property.

 

2 minutes ago, Spreadsheetman said:

Have you done a room-by-room heat loss analysis of the property?

I'm currently doing one using Stelrad Stars which has many different types of wall construction programmed in but doesn't do well with half-conventional ceiling half-warm-roof rooms and other unusual construction. If there's better software I'm all ears and will pay for it, as Stars is a pain to use.

[ProDave]

Most bird watchers hate the sparrowhawks, especially when one swoops in and snatches the little bird you were watching, as they do occasionally here and take one from the bird feeders.

[Sparrowhawk]

1 hour ago, JohnMo said:

As said new boiler will be leaps an bounds better as far as kWh used.  If you are replacing consider the rest of the system at the same time.  A 25 year old system will be full of debris from corrosion etc.  You may be better do a full re-plump or at least a power flush, then while you are at make sure the rads can heat your house at a low flow temps circa 30-40 degs. That will make the house heat pump ready, and you will benefit with even better boiler efficiency.

 

I plan to have the radiators replaced as we cannot bleed a few of them (either rusted shut or won't re-seal after bleeding), or they have no fins. I'd love to do a re-plumb however with engineered or laminate flooring in most rooms it would be an expensive exercise to lift and replace the flooring as well.

 

1 hour ago, JohnMo said:

Not sure doing a delta of 30 on radiators makes much sense.  Most modern boilers will manage the delta T, by modulation of pump output at high flow temps mine will give a delta T of 20, at low temps a delta T of 4.

I have got myself confused over flow temperatures and what to use. I've done the calculations for 3 rooms so far and assuming the worst-case of -2C outside and 20C (or even 18C) inside, I can't find radiators big enough for an average flow temp of 45C (boiler output 55/return 35).

 

I guess that's what weather compensation is for so the boiler then runs at 70/50 on those unusually cold days. So which temperature should I use for radiator sizing so that for most of the year I can run on low(er) flow temperatures?

 

As a check on my workings, for the lounge which currently has a 110x70cm double and a 155x55cm double radiator in the bay window, after entering the wall/window construction I have calculated

Air Changes (assumed)
1.5
Room Temperature
21 °C
Delta-T
24
Heat Loss Requirement
4114 W / 14047 BTU
Floor Dimensions
6.2m × 3.9m (24.18m2)
Height
2.55m

 

At delta T of 50 it's just possible to get big enough radiators in the same places as the current ones to meet that heat loss requirement. A modern Stelrad double 110x70cm is 2212W and a 1400x450 is 1919W. I can increase the height of one (and maybe raise the bay window windowsill to do the other) but how do I account for lower boiler temperatures at other times?

[SteamyTea]

Welcome.

 

If you are a practical sort of person, make yourself an air blower to depressurise the house. Will make finding, and sorting out leaks much easier.

There will be some in very unexpected places.

But remember it is where the air comes in from outside that is important, not where it exits into a room, that is just the physical symptom, not the cause.

[Sparrowhawk]

2 hours ago, Marvin said:

Hi @Sparrowhawk

 

The below is my overview.  Whilst I know you are going for a new boiler, the process below would still be the same. You will save a lot more over time fixing airtightness, the insulation and installing mechanical ventilation. Triple glazing is the most expensive element to install per m2 with the least energy saving(although important when everything else is high spec).

 

Normal double glazing with a U-value of 1.2 versus your triple glazing say high spec 0.6 U-Value. Inside temp 20 centigrade, outside temp zero C will give  a saving of about 10.6Watts per square meter. (ignoring any non air tight issues with the old double glazing window installation or the rest of the building) 

 

Thanks Marvin. I have learned an expensive lesson there. The noise reduction was maybe worth it (less sound of rain thundering on the Velux windows) but I won't be doing it again in a hurry.

 

AIM and APE are great acronyms. AIM will be my goal, and I am celebrating the slight condensation we now get on windows as a sign that the airtightness is better than it was 2 years ago.

 

As an aside on PV the roof isn't particularly suited, as it's hipped and the south facing aspect has a gable over the bay window which breaks it up and shades one side. I calculated 16 years for payback in September, which is longer than we plan to live here (esp if the house remains stubbornly cold!)

[Spreadsheetman]

7 minutes ago, Sparrowhawk said:

 

That is my fear that it is uneconomical to do anything about it. We have a cavity (filled with electrical cables) and all air bricks vent the cavity so in effect we have single-block-width solid walls around our property.

 

I'm currently doing one using Stelrad Stars which has many different types of wall construction programmed in but doesn't do well with half-conventional ceiling half-warm-roof rooms and other unusual construction. If there's better software I'm all ears and will pay for it, as Stars is a pain to use.

I built my own spreadsheet (similar to the one that gets posted on the forum quite often). I have also used Stelrad Stars, but it is inflexible as you say (and there are obvious missing features like the ability to duplicate a design). Good for coming up with a quick menu of rad choices though and was a useful sanity check for my own calculations.

 

For the house I bought recently an analysis showed me that adding insulation into the cavities was the big win. That saves 15% of energy at a stroke for a relatively small cost. Other stuff makes much less difference, but I’m making quite a few other improvements as a consequence of solving other problems.

 

Actually I think the CWI will make an even bigger saving in practice as I have closed up a vent hole through the cavity (old boiler air intake) and there was a considerable draft in there even when the outer brickwork was replaced so there is a lot of cold air movement round the cavity. There are no deliberate air bricks or vents, so I think it is mostly down to the open cavity tops at the front of the house that I will be closing up.

 

 

[ToughButterCup]

30 minutes ago, ProDave said:

Most bird watchers hate the sparrowhawks, ...

 

I rationalise a raptor strike as 'weeding out the weaker / older / infirm / stupid ' ones. Watched a pigeon being hit by a peregrine once : a feathered  explosion . 

[Sparrowhawk]

2 minutes ago, SteamyTea said:

Welcome.

 

If you are a practical sort of person, make yourself an air blower to depressurise the house. Will make finding, and sorting out leaks much easier.

There will be some in very unexpected places.

But remember it is where the air comes in from outside that is important, not where it exits into a room, that is just the physical symptom, not the cause.

Thanks @SteamyTea! Is there a guide I've missed on this forum? I've seen old car radiator fans mentioned as suitable - are there any others?

 

When I removed a 'strip of shame' (plastic gap-fillers between the wall and window frame) around the double glazing I discovered that not only was it open to the cavity behind them, but the double glazing hadn't been foamed into place with flexible foam/any foam at all. I can imagine there are hundreds of air leaks round there.

[Sparrowhawk]

3 minutes ago, ToughButterCup said:

 

I rationalise a raptor strike as 'weeding out the weaker / older / infirm / stupid ' ones. Watched a pigeon being hit by a peregrine once : a feathered  explosion . 

I grew up near a birds of prey centre and regularly visited so I have a soft spot for them, and have become accustomed to birds will do what they will do.

I have much less sympathy with cats.

[SteamyTea]

13 minutes ago, Sparrowhawk said:

Is there a guide I've missed on this forum

Not that I know of. A few people have made some.

I think @ProDave used a large desk fan.

 

[Spreadsheetman]

34 minutes ago, Sparrowhawk said:

 

I plan to have the radiators replaced as we cannot bleed a few of them (either rusted shut or won't re-seal after bleeding), or they have no fins. I'd love to do a re-plumb however with engineered or laminate flooring in most rooms it would be an expensive exercise to lift and replace the flooring as well.

 

I have got myself confused over flow temperatures and what to use. I've done the calculations for 3 rooms so far and assuming the worst-case of -2C outside and 20C (or even 18C) inside, I can't find radiators big enough for an average flow temp of 45C (boiler output 55/return 35).

 

I guess that's what weather compensation is for so the boiler then runs at 70/50 on those unusually cold days. So which temperature should I use for radiator sizing so that for most of the year I can run on low(er) flow temperatures?

 

As a check on my workings, for the lounge which currently has a 110x70cm double and a 155x55cm double radiator in the bay window, after entering the wall/window construction I have calculated

Air Changes (assumed)
1.5
Room Temperature
21 °C
Delta-T
24
Heat Loss Requirement
4114 W / 14047 BTU
Floor Dimensions
6.2m × 3.9m (24.18m2)
Height
2.55m

 

At delta T of 50 it's just possible to get big enough radiators in the same places as the current ones to meet that heat loss requirement. A modern Stelrad double 110x70cm is 2212W and a 1400x450 is 1919W. I can increase the height of one (and maybe raise the bay window windowsill to do the other) but how do I account for lower boiler temperatures at other times?

 

My new place is on oil (boiler is almost new too) so I can’t run very low flow temperatures. What I have done is design for 70deg flow, 50deg return (60deg average at rads) so the boiler will properly condense. I have made all new or replacement rads k1 type and not allowed for the insulation improvements I am making so there will be a good margin.

 

If later I switch (or am forced to switch) to an ASHP then rads can be replaced with k2s to accommodate a lower flow temp.

 

I am in the fortunate position of being able to replace all heating pipework though and replace most rads as we are eliminating all pipes in the concrete floors downstairs as part of the renovation process.

 

[SteamyTea]

1 minute ago, Spreadsheetman said:

so I can’t run very low flow temperatures

You can, just do it via a buffer tank or thermal store and a mixing valve.

The boiler will still condense then.

[JohnMo]

1 hour ago, Sparrowhawk said:

Air Changes (assumed)
1.5

 

Just looked at my SAP report and for a house with a 7 ACH @50pa, the actual infiltration rate is 0.4217.  So I would lower the ACH down to 0.5, instead of 1.5.  that should lower your losses quite a bit.  At the moment your lounge heat loss is 25% higher than my whole house, so doesn't look right.

[Marvin]

2 minutes ago, JohnMo said:

 

Just looked at my SAP report and for a house with a 7 ACH @50pa, the actual infiltration rate is 0.4217.  So I would lower the ACH down to 0.5, instead of 1.5.  that should lower your losses quite a bit.  At the moment your lounge heat loss is 25% higher than my whole house, so doesn't look right.

That's twice my whole house heat requirement at minus 3 centigrade outside and plus 23 inside. Eight times the loss per m2 floor area of mine. (104m2) Something needs seriously fixing!

[Iceverge]

Pump the cavity with closed cell foam.

 

Insulation and airtightness in one shot

 

You could drill from the outside to align the airbricks and put in ducting to maintain ventilation. 

 

Polyurethane foam won't degrade the plasticiser in the wires, although I think this risk of EPS beads is large theoretical. Similarly cable heating. A relation of mine did their cavity about 10 years ago. Plenty of wires in there and no ill effects.