HEATING AN INSULATED SHED??

[Ron_UK]

Hello, again

I'm at the final stages of designing my shed which is going to be an outer games room complete with pool table, bar and arcade machines.

It will be a 29 sq/m floor area shed with 75mm of Polystyrene EPS to the Walls, Ceiling and floating floor. 18mm Ply to outside and Plasterboard to inside.

The whole room will be completely sealed, 1 double glazed door to the front and one to the back with slight ventilation.

My worry is the Polystyrene can keep things cool as well as warm. If i do not heat the room constantly, its going to be blooming cold inside!

I want it at a temperature where i can play pool with a jumper on, not too warm but comfortable.

As the Walls, Ceiling & Floating Floor are Insulated with 75mm EPS, i'm hoping the use of a blow out heater on for say 5 mins every hour will make a nice ambient temp but not sure if i'm correct?
Will the shed hold the heat?

Any advice much appreciated.
Thanks
Ron

 

[JohnD]

It has very little thermal mass so the temperature will be very quick to rise and fall with a fan heater. This can encourage condensation on the things inside.

I would go for a small oil-filled heater at each end, which are slow to heat and slow to cool, using a room stat on the heating circuit. As winter draws to a close you will find retailers shifting remaining stock at good discounts. Oil filled heaters are also very unlikely to start a fire, as might happen if e.g. paper or cloth fell against an unattended fan or convector, or something was left close to it.

If you have glazing facing south, you will have solar gain even on clear winters days, but you will not want undesirables to be able to see in. Best if it looks like a garden shed from outside. Remember to add an alarm that sounds in the house as well as at the outbuilding.

 

[Ron_UK]

Hi John

Many thanks for your comments.

Thinking about it i must agree with you, fan heaters are great to build heat quickly but turn it off and the heats vanishes pretty quickly.

I like your idea of a heater at both ends of the room, it makes sense.

Like most of us i really need to keep the monthly cost down of heating the room. I'm guessing the oil heaters heat up and then switch off for a period of time, i've never used them.

Lol, what's my chances of burning just 1kw per day?

Cheers
Ron

 

[theprinceofdarkness]

See :- http://en.wikipedia.org/wiki/R-value_(insulation)#U-value
Area of floor = 29 sq. m
Area of floor = 29 sq. m
Area of walls = 44 sq. m ( 6m long X 5 m wide X 2m high)
Total area = 102 sq. m
EPS = .7 sq. m / W for 1 Degree C
So W = Degrees X 70. (100 sq.m)
This means that if its -10 degs outside and you want it 16 inside you have to make up 26 degs, so you will need 26 X 70 = 1800 W.

You can trawl through the various tables to get your actual figures, added insulation factor for plasterboard, outer skin etc. Also you can find out the added heat loss of windows and doors.
As for the summer, you might get solar gain, sunlight coming through the windows. You need external shading to stop this heat build up, curtains will not work, because the heat has all ready got into your room. Best thing to door is to cool the building down at night by running a inlet/outlet fan to use the cool night air to reduce its internal temperature.
Frank

 

[Ron_UK]

Hi Frank

WOW! Many thanks for all that info, i'm going to check it over now.

Somehow my 1kw per day is looking laughable!
Oh dear, time to grab the calculator.

Thanks again for your help, much appreciated.
Ron

 

[Ron_UK]

Hi Frank

So if its say 0 outside and i want it 16 inside, its just 16 x 70 = 1250 Watts per hour? Less if you use Oil Radiator i guess?

Oh yes, i've already drawn in me wall fans

Cheers
Ron

 

[theprinceofdarkness]

Yes. Oil filled is good, no flammable surfaces to set things alight. But when it comes to electric power consumption watts is watts.
Turning those figures over in my head , they seem too low, I'll revisit them!
Frank

 

[Ron_UK]

Hi Frank

Just need something to take the chill off really, just to make it comfortable.

Well we currently pay 12.2p per KWH with British Gas.
Even at 1kw per hour it works out at £89 per month!

Half that for say using oil radiator and its £44.50 per month if i'm lucky.
These figures i know are not 100% but just to give me some idea.

Heating is expensive any way you go, its hard to get lots of heat for little money i agree.

Cheers
Ron

 

[theprinceofdarkness]

"So W = Degrees X 70. (100 sq.m) " WRONG *
Should be W = degrees X 100/.7 = degrees X 140
This means that if its -10 degs outside and you want it 16 inside you have to make up 26 degs, so you will need 26 X 140 = 3600 W. Or for 0 degrees 16 X 140 = 2240W

* Trying out the best insulation from the Wiki site (5.2- 8.8), say 7 would give you 100/7 = 14 X 26 = 364 W, That's better, I got my sums upside down!
Sorry about that.
Frank.

 

[Ron_UK]

Hi Frank

No need to apologise, i really appreciate your time and help.

Its a large area to warm up and keep warm. Amazing how many watts are required to maintain a good temperature.

We pay our Gas monthly and it works out £85 approx a month to heat the whole house.

So i was hoping to heat a single room in the garden by electric would be much much cheaper, its surprising that its not.

Thanks for checking those figures again.
Cheers!
Ron

 

[Ron_UK]

I think these posts will help a lot of other people trying to heat sheds.

 

[big-all]

i would definately go for a fan heater as it directs the heat
it will heat up far far quicker than an oil filled radiator you dont loose heat any quicker its just warms the area its aimed at first [where you want it]
do not consider a naked flame like parafin or gas as you get load off condensation

 

[theprinceofdarkness]

Well you don't have to heat it for 8 months of the year? At a first very coarse estimate work out its volume and the volume of your house and then just pro-rata it. i.e. if its 10% of the houses volume, then the bill for heating will be 10% of the houses (+-30%?).
Ignore any figures for efficiency of oil filled radiators, they are fiction. the only difference is that all electrical heaters are 100% efficient, even light bulbs . With gas it might be different because I would think that the gas boards figures are for the heat supplied in your gas and not what comes out of your radiators. So for an old fashioned boiler with an efficiency of 60%, to get 1KW at your radiator you have to burn and pay for 1/.6 ~ 1.6 KW of gas. If you have a condensing boiler for your 1 KW in the radiator you must use 1.1 KWs of gas.
Going back to the 4 months heat usage, if you are not in the games room you don't have to heat it, just keep it warm enough to stop condensation forming, say 10 or 12 degrees C, then turn the heating up when you are in it. So now your heating is on say 4 months at 12 degrees LESS actual usage time, say 100 days at 4 hours a day, with the 100 days times 4 hours at 16 degrees. It would be a good idea to have two thermostats with a change over switch between them. So heating "off" would select the 10 degree stat and heating "on" would select the 16 degree stat.
Another thought comes to mind, your summer ventilation fans, cut a plug out of your foam with a piece of plastic on one side of it, so come the autumn you can stuff the fans holes up and preserve your insulation
value.
Cor, isn't life complicated?
Frank

 

[Ron_UK]

I think with England being more often cold i tend to forget the summer months! However 2014 had a nice summer and warmer at the end of the year.

Your right, it just needs to be luke warm when i'm not around, just to keep things ok. Then i can give it a boost when i'm in there.

My brother inlaw has a full size snooker table in his shed but its something like 50 sq/M, its a massive shed. I'll have to give him a call to find out how he heats it but knowing him he's as tight as i'am, lol!

Most hobbies & interests cost money, i do not smoke so a little extra spend each month is worth it for a good man cave.

Big_All
I did like the idea of the Fan Heater, the thought of blasting the room with heat and then turning it off for a while sounds good but not sure how long the heat would last.

Its a project i really want to start and if all goes ahead i will post pictures from start to finish. Hopefully when all done i can give you the heating results

Thanks again for everyone's help, much appreciated.
Ron

 

[JohnD]

You do not need to heat it to 16C 24 hours a day.

If it is ventilated, and the indoor temperature is higher than the outdoor temperature, it will stay dry.

If you are in there for occasional short periods, you can quickly heat it extra with a fan or infra-red, but for constant background heat, and keeping it dry, the oil-filled will be better.