Single Skin porch - possible insulation, plastering

[Ashman2]

1970's house. My house and all houses in street originally prior to redevelopments had single (half-brick porch). Looking at mine the original parquet floor (I understand they laid the wood into bitumen over concrete) matches rest of house floor under carpets so assumed original porch.

The porch measures 900mm by about 2400mm with a pitched roof. One side is against the garage, and a 2400mm is against the house.

Now I understand that I have to tread a bit carefully in respect of building regs as porches can be exempted based on an external grade door to house.

The plan would be to create a space that can take coats, and shoes,etc (suspect they will get damp in there at mo). It's been skimmed with something that looks like an external render as is rough. I was considering insulating internally just the two external walls. As it is half brick, and I only have 900mm would the insulation required and airgaps mean the porch would become extremely narrow!

The previous owner did have a electric radiator in there but suspect that would need to be turned up to max trying to heat the half-brick wall (and outside?)

 

[theprinceofdarkness]

Sorry, what is your question? I guess its glazed above the brick wall, get a price for double glazing, halve your heat loss with no loss of space. Insulate the roof. See what others have done and how much it has cost them.
Hanging coats in a porch, bit of a temptation?
Frank

 

[Ashman2]

Appologies, the wall has a circular window (appox 60cm). Question was whether it would be worth insulating or not worth it for the loss of space.

 

[theprinceofdarkness]

As the parquet floor is in good nick, I guess the construction is watertight?, if it is I would go for foam backed plasterboard, just screw it on and plaster. See :- http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1921
The U value is the number of Watts needed to keep a degree difference across a square metre. So if its 0 degs C outside and you want it to be 16 degs C inside, the amount of watts you need to heat one square metre is 16 times the U value. There are about 8000 hours in a year, so you could guess and say that you need 16 X 8000 X 2/12 hours in the winter and 8 X 8000 X 3/12 for the spring and autumn. So now you can work out your heating cost on the basis of the U value for a single brick skin (electric watts cost about £.15 for 1000). Hunt around on the internet to find the U values for insulated plasterboard and repeat the calculations for different thicknesses of foam. So you invest more in money, loose more space but save more money. Its up to you to determine where to draw the line. The cost of replastering will be the same for any new plasterboarding.
Frank

 

[^woody^]

It's totally pointless and a waste of time and money to insulate a porch.

 

[Ashman2]

Noticed a few cracks in this single skin porch. This is renderred cement internally. After getting the windows and door replaced the cracks are probably a bit wider just smaller than 10p thickness in stepped pattern from the window. The previous wooden door (opened inward left hung) and window were letting in water so the floor was almost saturated in wet weather . Internally the plaster is fine. The cracks all lead diagonally towards the corner where the door was letting in the most water, and from the point where a crack in the wooden window join was. They don't run all the way though just from the window corner diagonally to the door fame.

Any ideas for strengthening this wall? Dad said knock it down lol!

The roof is pitched

 

[motorbiking]

I think I'd be tempted to go with 20-40mm celotex or similar on the roof and external walls. You can't do much about the floor. The alternative is to apply insulation to the outside of the wall. I don't think you can ever justify insulation in terms of fuel cost savings (unless you are lagging pipes or upgrading loft insulation), but you can in terms of quality of life, time taken to heat your home, draft reduction etc..

The original part of my house is 9" wall - each time I decorate, I strip back the plaster to brick and install 25mm celotex and plasterboard. Even 25mm makes a big difference.

 

[endecotp]

I think I'd be tempted to go with 20-40mm celotex.

motorbiking, note that the question about insulation was from months ago. He's now asking about repairing cracks.

 

[Ashman2]

I think I'd be tempted to go with 20-40mm celotex or similar on the roof and external walls. You can't do much about the floor. The alternative is to apply insulation to the outside of the wall. I don't think you can ever justify insulation in terms of fuel cost savings (unless you are lagging pipes or upgrading loft insulation), but you can in terms of quality of life, time taken to heat your home, draft reduction etc..

The original part of my house is 9" wall - each time I decorate, I strip back the plaster to brick and install 25mm celotex and plasterboard. Even 25mm makes a big difference.

Yeah I should probably start a new thread as I'm confusing things!

I did do the calcs (although I need to check them as not sure I included the roof heat loss) and yeah around 40mm. I was thinking if I did the work to cover the crack I'd use 52mm U channel, 50mm C stud galvanized steel and wedge/force the 50mm celotex in there and board it. Planned to get out there to a shop to see if I could wedge it in!

Still in my mind there's still the vapour problem, and the circular 600mm window reveal. I did see a circular window former from expamet and thought maybe I could cut the insulation to 600mm circular . Still have a feeling this will be a right pain and look like cack at the reveal.

The walls have previously been painted with masonry paint so suspect if the water gets through it would get trapped behind the insulation- blackmould?

 

[endecotp]

Are you still seriously considering insulating the porch?
Unless you have heating in the porch, there is no point.
How did you create that graph? What assumptions are you making?

 

[Ashman2]

Are you still seriously considering insulating the porch?
Unless you have heating in the porch, there is no point.
How did you create that graph? What assumptions are you making?

I don't have the exact calc' I used for the single brick width but those below are roughly the same as those in the chart. For the insulation I used the celotex PL4000 data and just changed the insulation entry for each thickness. It's crude as there's no allowances for heat loss through the floor, and roof. If I guess at +50% that would put heat loss at 1000W.

The previous owner put in a 60W tube heater which I thought was odd because my gut feel suggested it'll be woefully inadequate. Though as upthread to heat it would cost £ and be a waste. In this hot weather the walls in there are hot to the touch so assumed the reverse in winter.

Anyway I wanted to run the numbers or atleast at best a crude estimate.

1.bare wall
>wall at U value 4.54, R value of 0.22
>celotex 4040 (40mm+12.5) 0.54, R value of 1.85
>temp change of 20C
>area of 7m2(I did forgot the roof, and the floor) (0.95m*2.4m) + (2m*2.4m)
>so 2.27*20*7
=636W

2.with the insulation
>total R value of 2.29
>1/2.07 *20 * 7
=68W

 

[endecotp]

The previous owner put in a 60W tube heater

Why? What do you do in your porch that requires it to be heated?
(Tender pot plants maybe?)

temp change of 20C

Again, why?

 

[endecotp]

1.bare wall
>wall at U value 4.54, R value of 0.22
>celotex 4040 (40mm+12.5) 0.54, R value of 1.85
>temp change of 20C
>area of 7m2(I did forgot the roof, and the floor) (0.95m*2.4m) + (2m*2.4m)
>so 2.27*20*7
=636W

2.with the insulation
>total R value of 2.29
>1/2.07 *20 * 7
=68W

That's not very convincing; why does "1. bare wall" mention celotex? Where does the number 2.27 come from? etc.
Might plausibly be the right final answers, but no points for showing your working.