Advice on heating our porch / insulation please

celerity

We have an unheated porch which is the only means into our house.
It is approx 2mx2m and has a door on each wall.

I'd like some advice on how to heat or insulate the porch in the most efficient manner for the benefit of the main house (not the porch).

The north and south doors are exterior ones. The front door is brand new with pretty good insulation. The back door is older, with more glazing and I'm sure less insulation, but isn't obviously bad enough that we've felt the need to replace it.

The east and west doors lead to my office and main house, respectively. Both are cheap interior doors with a large amount (70%?) of single glazing. I've fitted foam along the sides and draught excluders to the bottom, but they are essentially just panes of glass.

The porch, as mentioned earlier, is unheated, but this weekend I packed insulation into the loft space above it. It's too small to actually get into so I used a broom handle to literally jam it full to the rafters - so it has about 3' of insulation in the roof space now!

Last night, the temperature in our kitchen (about 12' along the hall from the porch) was 20C and in the porch it was 12C.
So, there is (unsurprisingly) a big heat differential between the porch and the house, and I'm conscious this is wasting heat from the main house both from conduction (hot house air hitting the cold porch door) and also convection (whenever the door leading to porch is opened and we get a big draught).

My question is whether to buy new doors to replace the interior ones, or whether to put a small radiator in the porch.
I really hate the idea of burning oil to heat an area of the house we just use as an entrance, but I've had advice from a few people that it's more efficient to keep it at a slightly higher temperature. I can see that argument, but I don't know how to even do back-of-a-beermat calculations to work out if it would indeed be cost effective. My gut feeling says that for such a small space, it would lose most of the radiator heat as soon as someone opened the front door?

In terms of new doors, I contacted some door companies to ask the U values of their internal doors but they've told me they don't have these figures as internal doors aren't designed for unheated boundaries. So basically they've told me to get external doors fitted instead - is that fair advice?

Sorry for the long post on what is probably an easy question, but you can probably tell I am a bit confused as to the best option! I don't have unlimited funds so I'd like to get the best "bang for buck" saving I can .

Thanks,

/\dam

rogerblack

celerity wrote: »

We have an unheated porch which is the only means into our house.
It is approx 2mx2m and has a door on each wall.

/\dam

Can't get a clear picture from what you write.
Fundamentally - how many square meters of what sort of structure are there.
4 square meters of single pane glass, or a windowless single skin brick structure...

celerity

Sorry, here is a wonderful diagram :

>--2m---<
    
***SSS=**   ^
**     **   |
E       W   |
E       W  2.3m
E       W   |
**     **   |
***NNN=**   v

Walls:
* : brick cavity wall
= : UPVC narrow glazed area next to door (brick near ceiling)

Doors:
SSS : External, south facing, 50% glazed, old but serviceable
NNN : External, north facing, 10% glazed, new
EEE : internal, 80% single glazed, draught proofed, leading to office
WWW : internal, 80% single glazed, draught proofed, leading to kitchen

Does that help?

/\dam

Martyn1981

Hiya Adam, long time no see etc.

Done a few things similar. Replaced the single glazing (6 units) in the door and panels between the living room and conservatory with double glazing. Got 3 (2ft by 3ft) units, and 3 (2ft by 1.5ft) units for £180. Sorry to mix measurements, but these were 14mm units. I did all the woodwork.

Door from kitchen to rear pantry area (which is unheated) was going to do the same, and remove the upper wood panel and fit some DG to see out as external UPVC door has glass panel. However decided in the end to replace the internal panel door with an oak external door, as the DG might have been a little fat for the recess, and you don't want it falling out after prolonged use.

So, could you swop the glass in the internal doors, are they wooden, are they thick enough, can you find a supplier that will do a thin DG panel (I think 12mm is possible). If you have to swop in an external door, is the frame wide enough, will you have to alter some of the woodwork such as door jams, can you do this yourself, including fitting hinges and locks/handles or will you have to pay to have it done?

Whilst the inner doors may not be perfect, the porch will at least act as a buffer between internal and external temps. For instance in the winter when the living room is say only 15C before heating comes on, and outside is 0C, at least the conservatory is 5C, so some thermal buffer at least.

Sudden thought, if doors are mostly glass, then the weight will increase quite a bit, so if you DG them, you might want to fit an extra center hinge (if there isn't one) or replace the existing hinges with slightly larger ones that have more screwholes.

Mart.

rogerblack

Oh - right - I wasn't considering a structure with four doors in it!
The floor is presumably uninsulated too - a substantial amount of heat will be leaking out there.

The 'easy' solution is to simply treat it like an unheated space.
Two external doors to replace the internal.
I assume there is no spare vertical space to insulate the floor?

Are the east and west walls part of a heated structre, and the only unheated walls the north and south 2m with a door in them?

Draught sealing will be majorly important, with two external doors in a tiny space.

Firstly, you need some idea of the thermal performance of the structure.
On several consecutive nights of similar external temperature and wind.
Put a 500W or so heater on for 24 hours, and off for 24 hours, and see how much the temperature varies.

celerity

Thanks Martin, yes I often absent myself from these forums for months at a time but inevitably return to see what is going on .

To be clear, I have no DIY skills (beyond shoving loft insulation with a broom handle anyway) so would be paying a skilled artisan / local cowboy to do any work for me.

Are solid oak doors particularly good for insulation or would a modern UPVC door be better? I went to visit an eco house a few years ago and the porch door they had closed like a thing of beauty - it had amazing seals around every edge. I'd very much like something like that but so far I haven't seen any door companies that discuss this. Are the seals something that the installer adds separately?

I've done a bit of reading since starting this thread and am beginning to think that the "putting a small heater in your porch saves you money" idea is a myth - albeit an oft-repeated one. I've even found one thread that suggested heating a porch is such a bad idea that it might be against building regs?

/\dam

Martyn1981

Adam - please don't heat your porch! Aside of course from Roger's test, that's a really good idea (wish I'd thought of that).

Wood looks nice, but a well fitted UPVc door will give a really great seal, and added security if you need it. Plus less maintenance.

Mart.

celerity

rogerblack wrote: »

The floor is presumably uninsulated too - a substantial amount of heat will be leaking out there.
I assume there is no spare vertical space to insulate the floor?

Correct, and the floor tiles go through seamlessly to the hall and kitchen beyond. That said, I wouldn't necessarily be averse to ripping up the porch only and giving that a different floor.

The 'easy' solution is to simply treat it like an unheated space.
Two external doors to replace the internal.

That's what I'm leaning towards. I was thinking of getting a fire door with no glazing for the office though - would that have a similar U value to an external door do you think?

Are the east and west walls part of a heated structre, and the only unheated walls the north and south 2m with a door in them?

Yes, east opens directly into my office, which is heated with a wood stove (when the office gets too hot I open the door and heat the porch), West leads into the kitchen which is inadequately heated by small radiators - but the house is open plan and it gets a lot of heat from the lounge wood stove.

I should add we are in a bungalow with cavity wall insulation and 30cm insulation in the loft.

Firstly, you need some idea of the thermal performance of the structure.
On several consecutive nights of similar external temperature and wind.
Put a 500W or so heater on for 24 hours, and off for 24 hours, and see how much the temperature varies.

I've just bought a 600W oil radiator which should do the job.
Could you please explain your reasoning depending on what I might find? Wouldn't opening the external doors during the "no radiator" test mess up the results?
We regularly open the back door to let our dog out...

Cheers,

/\dam