i have just gutted a four bedroom townhouse over threes floors - ground / first and attic.
i have therefore to decide what heating / hot system i should put back in as there is nothing right now - not even a copper pipe!! there is mains gas and electric.
it is of 1950's construction, so the walls are not very well insulated - the roof is well insulated. i am thinking of a radiator system as i am on a limited budget and underfloor heating will be too expensive.
water wise - there are three showers (1 on each floor and it is likely that at least two will require water at the same time. there is also a bath on the first floor but unlikely to be used much.
there's plenty of space to mount pretty much any system but i really don't know what's best - probably most concern is the demand for hot water - a simple combi boiler could not handle it. and i only want one electric shower as an absolute emergency.
i should say that i don't expect to live in the property for more than 5 years at the most so i do not want to pay huge amounts for a renewable energy system that takes years and years to re-coup the investment.
any advice gratefully received. thanks
Doubtless you will receive plenty of conflicting advice, but, given that
you have gas, I would go for a traditional gas boiler and showers fed
via a large hot water cylinder with immersion heater for emergencies.
Other will advise on calculation of boiler and tank sizes - take the
advice and add 10 per cent.
Our system is oil fired but otherwise as above. Plenty of capacity for
the traditional radiator central heating, plus hot water. The water is
heated twice a day, for one hour early morning, and another hour mid
afternoon. Two of us shower in the morning, and one in the evening.
Very occasional baths. We never run out of hot water.
Two caveats. One, I'm biased and hate combis, and Two, although we have
several showers in the house, for no particular reason, we rarely seem
to run more than one simultaneously.
On Tuesday, 8 March 2016 08:29:59 UTC, News wrote:
However, as combis are often cheaper than corresponding non-combi versions,
you could use the combi hot water for one shower, or the kitchen tap, whic
h will give you instant hot water in that location without waiting for the
cylinder to heat.
If you're only going to be in the house for <5 years then you might conside
r whether the additional cost of an unvented hot water cylinder is really n
ecessary. Put the electric shower in the attic, and you may find you have e
nough head from an attic tank to give adequate showers on the ground and fi
rst floors without needing pumps - they'll be low pressure but you can get
For zoning, consider putting the bathroom towel rails on one zone so you ca
n have them on in summer for drying towels without heating the rest of the
+1 (although I am on gas and only have one shower).
If you are not going for a mains pressure cylinder (more expensive, more
to go wrong) you will benefit from a double impeller shower pump for the
top floor. Don't economise, get a Stuart Turner. I suspect that a single
3 bar pump might be sufficient for all three showers. Certainly I
normally throttle the flow on my 2 bar one. Might be worth plumbing the
shower feeds in 22 mm?
On 08/03/2016 07:49, firstname.lastname@example.org wrote:
If you have a conventional system with a hot water tank, then you can
have an immersion heater for use if the boiler fails or you want to stop
it for any reason.
OTOH If you have cold water tanks in the roof you need to ensure that
the water does not freeze in the winter, especially if the house is left
Another issue is whether you have a system boiler. These are more
complex, presumably cost more and are more tedious to fill. OTOH you
have to install a header tank for a conventional system.
My fully pumped conventional system uses fully motorised valves which
don't move if the programmer switches the heating off and on to achieve
I am not a fan of thermostatic radiator valves. I would regard a wired
in programmable thermostat as essential, preferably with remote control.
Many programmable thermostats are single channel. OK for the CH but I
like to have the HW off when it is not required.
Other points I would add:
a) Use radiators with a rounded top rather than a welded seam.
b) Install a heated towel rail in the bathroom.
c) Install drain points in the pipework to each radiator that won't
drain without one.
d) If you have a hot water tank, get one with 50mm insulation on it.
Mine heat towels better than heating the room. Probably just me.
A new boiler will cost £4,500 + gas costs.
For mere amusement, over 5 years could it be cheaper on electric with
ceiling fitted infra-red panels, room occupancy sensors and much better
room insulation fitted?
On Tuesday, 8 March 2016 19:37:30 UTC, Michael Chare wrote:
on a limited budget you could check out the boilers on ebay. Should save you most of a grand.
gas boiler & cylinder then. Again there are used cylinders around at times.
cheaper to add an immersion element
costlier to fix
TRVs are only semi thermostatic, not truly thermostatic. But it beats no thermostat on each rad. A separate real thermostat per room is certainly better, but if you'll be moving out I'm not sure the expense is warranted.
Bimetal stats are fine. Technology doesn't always produce a win.
pointless gimmicks imho. OTOH a future buyer might like it.
or place it where you can stick more than 2" of loft insulation round it.
On 08/03/16 07:49, email@example.com wrote:
First thing: do you have a cavity and is it insulated - if not, do that
Then big efficient radiators. Bigger than you think, subject to space.
Use the manufacturer tables to ascertain power output and then double
the size over what it needs to maintain steady state (or what you think
For little extra cost (ordinary rads are not expensive), it will:
1) Keep the boiler happy avoiding cycling;
2) Give you a faster warm up from cold so less unnecessary heating;
3) Allow the heating to run at a lower water temperature which is more
efficient on the boiler (upto a point) and more comfortable to humans
(usually - opinions vary).
For example - a house I have with 2" cavity wall blown fibre (old) and
3" celotex in the roof requires a total of about 3-4kW electric heaters
to maintain steady state 21C downstairs when outside is 5C ish.
However, it takes a day to 2 days to come up from stone cold with 4kW.
So I will be aiming to put in a total about 5 times that at least in
terms of max output power of radiators at the usual delta-T, then I can
drop the water temperature (and thus the delta-T) a bit too.
On the basis of what you've said if you have not got figures for how
lossy your house it, then I would aim for 3-4kW for a massive room (ie
really large lounge), 3-4kW for a large bedroom, 2-3kW for a medium
bedroom and 1-2kW for a tiny bedroom and so on.
And zone it, at least by floor.
You'll save more in rapid warm up when needed, then being able to turn
it off in unused areas when not than any amount of fancy wibbling with
heat pumps, solar panels and the like will ever give you.
On the subject of insulation, if you have no cavity, do you have the
space to put 1-2" celotex on the inside walls (at least external walls)
then plasterboard? Even 1" over bare brick will make a very large
difference to both comfort and heat loss.
I've found in both the victorian flat over our shop and our 1960/70
detached house with non insulated floors, when using the "radiator
sizing charts" they've always been wildly over sized. When I sized up
the radiators for the bedrooms at home to work with UFH flow temp. I
needed massive rads. So in the end based on previous experiences I
simply took the biggest single panel finned radiator that would fit in
the space where space wasn't a variable i.e. under windows (single so it
didn't stick right out into the room) and used radiators that "looked"
the right size in the hall and master bedroom.
All chuck out more than enough heat even with flow never exceeding 55
degrees MAX. to bring bedroom up to temp quickly.
Not a very scientific approach but one based on previous results of a
"by the rule book" sizing.
Wouldn't an over-sized radiator system make the boiler cycle more than a
system where the radiators are perfectly sized for all but the rare week
or 2 every 10 years or more when temperatures go into minus double-digits?
Easier to add an additional heat source in those rare and exceptional
conditions than to design a system with huge over-capacity that will
rarely be required.
It's all energy consumed. Bring it up to temp really quick with a high
input or slower with a lower input. A steadier and more constant lower
heat input would be preferable from a comfort perspective.
Weather compensated Boiler keeps temp nice all the time. With UFH it
means the floor is always just right. If I push 55 degrees around all
the time, the floor goes off and cools rapidly (between joists so no
thermal mass) which means a floor that's cold long before the room stat
has dropped to it's low set-point to fire up the zone and re-heat the floor.
Definitely. And weather compensation is an absolute must-have for both
economy and comfort.
When would you ever need to heat from stone-cold? I'd always leave the
heating set to perhaps 15 degrees if I could be arsed to re-program all
the room stats which I wouldn't.
Interesting and useful. I'm at the 'pre-planning' stage of modernising
my late mother's bungalow. Two medium sized bedrooms, kitchen,
bathroom, front hall, back lobby, L-shaped footprint, the lounge/diner
and one bedroom have three outside walls. Urea-formaldehyde foam
insulation in the cavity, installed ~1975, a thin scattering of
vermiculite in the loft, to be replaced by something effective. Mild
climate. Central heating and plumbing both need completely stripping
out and modernising. I'll be getting it all done professionally, as
there's quite a lot of other stuff to do as well.
You say about a boiler "Use the manufacturer tables to ascertain power
output and then double the size over what it needs to maintain steady
state (or what you think it needs)", and you also give ball-park
suggestions for the wattages needed to heat some rooms, e.g. 3-4kW for
a large bedroom. Do those figures include the doubling factor, or
should I double up the sum I get for the bungalow, which is
approximately 18kW on the basis of your numbers as they stand? I must
say, doubling that to 36kW seems a bit excessive for a small bungalow.
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