Can I afford to heat my Garage?

[Iain DownsParticipant @iaindowns78295]

As the weather has turned, I am unable to get into my shed and it looks like I will suffer on and off now until spring :(.

I do have a fan heater in there, but if I turn it on when cold, all my machines end up dripping in water which I think is a bad thing – I go in down to 10 C or a bit lower, but any colder is just too much.  So I’ve been wondering what the cost would be to keep the heater turned on (at 10 – 15 degrees).

I expect it will be unaffordable, but would like to check.  I want to work out the U values (or R or thermal loss or whatever) of the garage, but have been unable to find any such specifications for the precast panels that the garage is made from.

I was hoping that a member happened to be an expert in such things and could at least point me in the right direction!

The garage is a straightforward 2.4m x 4.8m thing with a couple of double glazed plastic windows, a steel door and a pitched concrete corrugated roof.

All of my searches have ended up telling me HOW to insulate the damned thing which I agree I should have done before sticking panels to the walls (to hold tools and benches), but it’s a bit late now! It would be doable, but not in the winter and not easily 🙁

Thanks in advance,

 

Iain

 

[JasonBModerator @jasonb]

assuming panel is 50mm thick U value is about 32 depending on the exact mix

EDIT should be 3.2, got a decimal point in the wrong place for the K value.

[JourneymanParticipant @journeyman]

The simple answer is no, unless you have a lot of spare cash. It is fairly pointless heating an uninsulated building, you will lose heat as quickly as you can put it in. You may as well put the heater in the garden and try and heat that.

First job is to add insulation to the roof and the steel door lets heat or cold travel through it without  even slowing it down. I have a wooden shed 2″ rockwool in the walls and 4″ in the roof. A 1kw fan heater with thermostat keeps it comfortably at a steady 12C and more importantly no condensation on the machinery which is the main reason for me to run the heater. No rust no problems. To be honest I haven’t worked out the cost but it has to be better that replacing tools and machinery. The heater only runs for a relatively short time before cutting out.

If I want to work there I turn the heater up a bit. Doesn’t take long to warm up. Must of course remember to turn it down before leaving.

Table of u-values here – Combustion Research Corporation

John

[SteviegtrParticipant @steviegtr]

 

I fitted a Chinese diesel heater in mine last year & so far it’s been a godsend. I have now found Kerosene at £1 per litre & it uses very little. Been 100% reliable You can even set a timer on it. Some of this forum’s members shun them but many of them have them. I sold my classic Suzuki 2 weeks ago & the guys that picked it up were Marine engineers. They saw the heater & said most of the boating guys have had them fit these for them, because of the cost of Eberspacher & Webasto being so expensive.

They also told me of the many they have fitted only a couple had broke down. The little fuel filter can go & the glow plug can fail. I have not had any such problems but parts are very cheap for them & everything is available.

Steve.

[Ady1Participant @ady1]

I’m in a solid concrete/brick garage and work down to zero degrees ok

I don’t heat the garage, I heat me

I dress like a hillwalker without the goretex coat

I have a flat bit of chipboard to stand on if at the lathe or anything for a while

Cleaning and shifting stuff about warms you up

Cold conditions are good for electrical stuff because it won’t overheat easily plus the heat helps

Being a bit fat makes a massive difference for circulation, especially the hands

Below zero and it starts getting tough, I tend to call it quits at that point unless I’m super-keen

A good hearty lunch before starting also helps because you want to work it off

[BazyleParticipant @bazyle]

Put small tube heaters under each machine and a COTTON sheet over the top followed by a blanket to form a microclimate. Heat all machines before you go in for a work session until they are some 5 degrees at least warmer than ambient. Then only uncover the machine you are going to use and direct some extra heat at it to reduce the condensing of your breath.
When a damp warm front comes by, as will happen in a few days, turn on the heaters even if you are not going in there.
Concentrate your initial efforts on sealing every possible draft to keep keep moist air out when it will become viable to run a dehumidifier. Because this is a form of heat pump it will provide more heat than the energy you put in.
You could also consider partitioning off a small section like around the bench even just with plastic sheet or old curtains so you only heat a tiny area. Use a radiant heater that heats you not the air.

Back to the original question of U value for concrete panels. I’ve never dealt in Us only conductivity. A simple rule of thumb is that an 11in cavity brick wall is about equivalent to 1inch of expanded polystyrene. A 9 in solid brick wall is about half that. A concrete panel barely an inch thick is only a wind break.

[Ady1Participant @ady1]

My dad worked one winter in a cavernous concrete floored machine warehouse in Birmingham in the 50s. you stood on a wooden board to stop yourself getting chill blanes

50 feet up in the roof by the skylights was a glowing 1Kw bar heater to meet H&S heating regulations for the shop floor workers

luxury

[Pete RimmerParticipant @peterimmer30576]

A 1kw bar heater 500 feet up would never have met regulations because there is no specific requirement for heaters, nor any specific cold temperature limit for working, only a guideline indoors temperature of 16 degrees or 13 degrees for strenuous work. Employers have a general duty of care to control risks including exposure to extremes of temperature but this is a matter for the employer to risk-assess and take appropriate measures as they see fit. Whether the measures they apply are actually adequate “so far as is reasonably parcticable” will only be tested in the even of an audit, inury or claim.

[Nigel Graham 2Participant @nigelgraham2]

I would advise against using any open liquid or gas fuel heater in the workshop.

It needs a lot of ventilation to provide combustion air and to remove the exhaust (carbon-dioxide… or monoxide if it does not burn the fuel properly in which case it could kill you).

The exhaust is not only CO2. It is also water (as vapour), which you don’t want in a workshop!

‘

You’ve already hidden much of the walls behind benches, machines, etc. but presumably most of the roof is still reasonably accessible, so insulate that at least, followed by whatever you can of the walls.

If the building has any windows, double-glaze them. Even “secondary double-glazing” (e.g. polycarbonate sheet screwed to the frame with intervening draught-excluder strip) will help. Mine consists of double-wall box-type roofing sheet bolted to the outside of the shed’s large, thin glass windows. Not strictly double-glazing and it does reduce a lot of the daylight, but it helps by keeping the worst of the weather off.

I have though lined the concrete-block walls with 25mm foam board faced with “Stirling-board”, and fitted an insulated ceiling under the corrugated asbestos-cement roof.

Ivy from the neighbouring, neglected and now abandoned garden (occupier’s death) is creeping across the roof and despite some risk of it penetrating the eaves, may add a little extra insulation the “green” way!

[Mike HurleyParticipant @mikehurley60381]

I must agree with Journeyman 100%.
My garage is similar in size & construction to yours Iain, detached, single brick. I did put in a couple of inches of insulation under the corrugated roof many years ago. and stuck odd sheets of foam on the inside of the metal garage door, and bunged ‘temporary’ stuff in any gaps that may cause draughts.
I have a 3KW oil-filled radiator in there, but it is only ever set on the 1KW range, with the thermosat set to about a quarter. I leave this on all winter, 24 hours a day. After the first few days I notice the chill is off the workspace and the thermostat’s red light only comes on occasionaly. Surprisingly for the last couple of years doing this, I didn’t notice any spike in the bills, compared to before, regardless of the physics / mathematics of energy use. If you have a dreaded smartmeter then itwould be easy to monitor real costs over a test period.
I also have one of those cheap little greenhouse air moisture meters on a shelf, and I check it for any reading of ‘Damp’ but never seem to get any issues.
The benefit is that all my tools and equipment seem to stay at a nice even temperature and don’t suffer condensation / rust and are comfortable to handle. It seems economical, enables me to work OK on all but the most severe cold days.
ADY1’s concept of heating himself only is fine if that suits. The only problem I find is keeping hands / fingers warm enough to do accurate work (well, accurate by my modest standards anyway). Horses for courses as they say.
Hope that helps.

Mike

[Matt TParticipant @mattt]

Upvote for bazyles idea, I’ve seen people make covers with thermostatic heaters in for smaller machine tools. I recently insulated the ceiling on my workshop and it’s made quite a big difference. I suspect fixing the gap between the roof and the brickwork helped too but I’m sure the insulation is doing good work. I run a small bar 80w bar heater right behind my lathe. I know it’s giving off about as much heat as a tea light but my workshop is really tiny. I put a sheet over the lathe when I’m done and run a fan heater while I’m in there for comfort (although I find myself flicking it on and off). Ceiling insulation is pretty cheap and relatively easy to install, if you’re in the notts area I have a bit left (probably 3sqm worth) I’m more than happy to let go and save the landfill.

[Howard LewisParticipant @howardlewis46836]

+1 for comments re heating an uninsulated building. the heat will soon disapper!

iN My former uninsulated ship, thge oil on the Myford would turn grey as it emulsified, unless heating was on.

A 2 Kw fan heater in the average uninsulated garage will be running almost full time once the ambient falls to 10C or below.

Insulation is vital.

The time, effort and cost of removing the existing wall coverings, and adding 50 mm of glass fibre behind it will soon be repaid, DITTO for the ceiling, and the door. (Polystyrene sheets would be a good alternative)

An electric heater should not cause machines to “dripm with water” since ni water vapour is being produced. Thehe condensation takes place because the air contains too much water vapour (humidity) and the cold machines are below the dew point, so the vapour condenses on to the cold surface. Once the machines warm to above the dew point, the condensation will evaporate, being in the air, rather on the machines.

Spending time in an poorly ventilated shop will increase humidity since we exhale water vapour with every breath (The human body is oxidising the hydrogen contained in our food (Carbohydrates) to produce water, which we exhale. And, to an extent, we perspire adding to the watr vapour and hunifity in the atmosphere).

So apparently, counterproductively, the space needs some ventilation, to allow the water vapour to escape (Heating the air will increase pressure in a totally enclosed space, so ventialation is needed to allow the excess to escape)

My small shop, insulated with 50mm glass fibre on  four walls and ceiling, is ventialted by two small grilles at floor level  and weatherproof fan cowl at ceiling level.

When frost is expected, a 60 watt tubular heater under the bench is switched on to keep condensation at bay. Afterr 24 hours, the steel bench feels warm to the touch, so helps to disperse heat into the shop.

HTH

Howard

[ChufferParticipant @chuffer]

My workshop is 4 metres x 2 metres which is part of my double garage. Fortunately the builders used it as a sales office so it is insulated on the external walls, has a ceiling with some insulation above and even coving!! When I had the internal walls put up to create the workshop I made sure that these were insulated. Consequently in the height of summer when it’s boiling hot outside walking into the relative cool of the workshop is a blessing. So, in my opinion as has already been said before attempting to heat a garage, or any similar building, insulating it has to be the highest priority.

Having insulated it how to heat it is the next question and this is where I would like some help. Ever since it was built I’ve heated it with a 2kw fan heater with a frost stat which has kept the lathe and mill free from condensation as well as the loco’s. However, every time I mention fan heater I get sharp intakes of breath and words that fan heaters should not be left unattended. I’m quite happy to continue to use the fan heater while I’m in the workshop as it heats up the area relatively quickly but think that because of its age it would be a good idea to get a heater which is in theory safer for use when I’m not there and the temperature drops.

I’ve had a search through this forum yesterday but couldn’t find a definitive answer as to the best way to go with a heater that is all but inert and safe. Because its a relatively small workshop, I’m a bit stuck for space but am coming around to the idea that a thermostat controlled electric greenhouse heater – basically a tube, might be the best solution. What do other forum members recommend?

Chuffer

 

[Harry WilkesParticipant @harrywilkes58467]

Iain having the same thoughts my self and if I do work on through the colder months I think I may got the route as steviegtr despite some of the adverse comments posted !

H

[Mark RandParticipant @markrand96270]

As a datum, I built my shed from structural insulated panels, which have 125mm of insulation between the inside and outside layers for all walls roof and door. The floor has 100mm of PS foam. The 30m^2 shed, with a 3.5m high roof needs about 5.3kWh from the heat pump/AC per day to keep at 19°C in the current weather.

That’s about the least you can expect to keep a shed comfortable for working in.

The split unit heat pump/AC is noticeably more efficient than an electric heater, but obviously, has a higher capital cost.

 

[BazyleParticipant @bazyle]

If you heat intermittently then a fan heater is a good option to heat the air quickly and you can direct it at yourself. Many new models have a safety switch for it falling over but don’t go for the ‘special’ ones in adverts trying to make you think somehow they provide more heat than any other electric heater. Rather disgracefully when ‘ceramic element’ heaters first came out a member of parliament actually recommended them in the chamber as giving more heat than a conventional one.
However it is when heating the air like this when your cold machines are most at risk from being the cold item to catch the condensation. This is where a number of low power tube heaters under machines will help.
For long term unattended heating an oil filled heater is safest. Probably the least effective is a simple convector heater as the heat just rises to the ceiling and then only comes down to you when it has cooled a bit.

The time to heat an unoccupied workshop is not when frost is coming as the contents will be warmer than the grass outside which thereby takes out the moisture from the air for a few days. The danger time when you need heat is in the hours before the inevitable warm (wet) front comes in and now your machines are cold so will get the condensation if you have failed to effectively seal the building. Once the air is all damp again turn on the dehumidifier.

[Steviegtr]

On Steviegtr Said:

 

I fitted a Chinese diesel heater in mine last year & so far it’s been a godsend. I have now found Kerosene at £1 per litre & it uses very little. Been 100% reliable You can even set a timer on it. Some of this forum’s members shun them but many of them have them. I sold my classic Suzuki 2 weeks ago & the guys that picked it up were Marine engineers. They saw the heater & said most of the boating guys have had them fit these for them, because of the cost of Eberspacher & Webasto being so expensive.

They also told me of the many they have fitted only a couple had broke down. The little fuel filter can go & the glow plug can fail. I have not had any such problems but parts are very cheap for them & everything is available.

Steve.

MAIB don’t think they are a good idea on boats.
https://assets.publishing.service.gov.uk/media/5f85ac6c8fa8f561ce5417d7/2020-SB2-Diversion.pdf

A particular issue, even without failures, is the silencers on the vehicle ones are not gas tight by design (condensate drain hole I think) so they leak cardon monoxide.
These heaters are not designed or approved for heating buildings. The cheap chinese ones probably have no valid approval for anything.

[Martin Dilly 2Participant @martindilly2]

Garage unheated, though one wall is the house; wooden up-and-over door, thickish wooden roof with tarred gravel on top, but no insulation. I soaked some old blankets in old engine oil diluted with paraffin and one gets draped over the lathe and another over the mill. Seems to have kept things rust-free for 15 years or so.

[SteviegtrParticipant @steviegtr]

Hi Robert, you are spot on. The guys I spoke to said most of the ones were replacements for the expensive to repair webasto etc. They said they use the exhaust from the existing heaters. They throw the supplied ones away. My friend did exactly the same. He had a Fairline Phantom 46. He was fed up with the heater failing & costing a arm & leg to fix. The marina he was in changed it for a Chinese cheapy. They also used the existing silencer setup from the old unit. So for once i do agree with you there.

There was a company who build Motorhomes & they did a full review of them The only thing they knocked them on was the alloy housing inside the heater was a bit rough cast. They also noted the Ebersp & wabasto units had a waterproof connection to the ecu inside , the chinese ones just had a standard plug & skt arrangement.

I can honestly say that I have been 100% satisfied for the little cost & how frugal it is. Especially as now i can get my Kerosene for £1 per litre. I just bought 50 litres. Which I am hoping will last all winter.

Picture from side of packing box.

Steve.

[michael howarth 1Participant @michaelhowarth1]

Don’t bother with heating the workshop. Heat yourself. Get a heated vest/jacket which runs on li-ion battery pack. Loads for sale on the usual sites for not a lot of money. I bought a Keis motorcycle vest and that keeps me toasty for 3-4 hours and £0.013p  cost per recharge of 12v 2600 maH battery. Going upmarket a bit, I see that Makita do a vest for about £130 which runs on 18V – plenty enough to cook you through andgive you a nice bit of crackling.

Mick

[jaCK HobsonParticipant @jackhobson50760]

I spent hundreds insulating my workshop – best investment I ever made.

I bought a heated waistcoat – about £30 plus battery. Second best investment, and much cheaper!

[Alan Wood 4Participant @alanwood4]

Use of the ‘Chinese heaters’ on a boat is quite different to the potential use in a workshop.  On a boat the heater will almost certainly have to be inboard whereas with a workshop the heater can be mounted externally and have just the hot air feed into the workshop and the return feed from the workshop.   Any combustion related issues are therefore completely decoupled from the workshop environment.  On this basis as a workshop heater, in a reasonably well insulated workshop, they work well with the air recirculated and most importantly relatively moisture free.   There is an example of an externally mounted heater on my blog.  I have also posted a design for a humidity monitor which could be used for turning on a heater or dehumidifier when dew point is reached.

[Chuffer]

On Chuffer Said:

Because its a relatively small workshop, I’m a bit stuck for space but am coming around to the idea that a thermostat controlled electric greenhouse heater – basically a tube, might be the best solution. What do other forum members recommend?

Chuffer

 

I’ve got 2 of these 80W Dimplex heaters from Screwfix.  They’ve got thermostats and I’ve set mine to come on when the temp drops to about 10C

https://www.screwfix.com/p/dimplex-ecot2ft-wall-mounted-tubular-heater-80w-713mm-x-81mm/1796F?tc=UT1&ds_rl=1241687&ds_rl=1245250&ds_rl=1249404&gad_source=1&ds_rl=1245250&ds_rl=1247848&ds_rl=1248151&gclid=Cj0KCQiAyKurBhD5ARIsALamXaF5G13WuEstSwqHQKWGPjww0-Nv3BKAYjz91Joii5RL4XQKsPbN4b4aAnEdEALw_wcB&gclsrc=aw.ds

Rod

[Robert Atkinson 2Participant @robertatkinson2]

While using a better exhaust and external mounting certainly help, they do not automatically make them safe. I’m not sure wrapping the air duct in bubblewrap, even on the inlet side, is a good idea. Rock or glass wool would be better.
A specific and potentially fatal failure on all this type of heater if cracking of the combustion chamber wall / heat exchanger. This allows toxic fumes into the airside. There have been several fatalities on aircraft due to this failure mode. Poor materials and quality control make failure more likely.  If anyone wonders why I am so concerned about this, I lost a relative due to CO from a incorrectly installed (DIY) heater. It is only a matter of ime before one of these causes a death. The cheap chinese e-bike and e-scooters have shown the danger of shoddy goods.

If you must use one of these heaters:

BUY AND USE a mains powered CARBON MONOXIDE ALARM.

[mgnbukParticipant @mgnbuk]

Another satisfied Chinese diesel heater user here.

I fully appreciate Robert A’s concerns about these units but, having previously experienced using a Webasto 5Kw unit supplied as standard equipment for heating the living space of a commercially built motorhome, I am happy that I have an installation that is both safe & fit for purpose. In terms of the user expereience I can detect no difference between the Chinese unit & the Webasto.

The supplied silencers do have a condensate drain hole, but as the silencer is outside the building that does not cause fumes inside the building. My unit is supplied by a 12V 20A power supply that is isolated when I am not using the heater & I do not run the heater when I am not in the building. I chose to take the combustion air from inside rather than drill another hole in the wall for the combustion air inlet, but the garage is not hermetically sealed & I have not noticed any adverse effects from working this way for 2 + years. The exhaust pipe (which gets very hot, so make sure nothing combustible can get near it !) exits the through a close fitting hole drilled through the concrete wall block. The air within the garage is recirculated through the heater. The garage is a stand-alone, single skin, Marshall’s “Heritage” concrete block built double with a tiled pitched roof, 2 steel “up & over” doors & no windows. The walls have been insulated internally with 20mm polystyrene sheets held against the walls with 12mm chip board & flooring fitted the the roof rafters to form a ceiling – I could (and should) do more from an insulation POV, but that is still on the “Round Tuit” list at present. As with the motorhome installation, a CO detector gives an indication of any contamination with combustion byproducts in the heated space should a heater fault develope. Having the heater unit inside the garage (but exhausting outside) it is a bit noisy from both the air circulating fan and the fuel pump, but not objectionably so and, unlike my experience trying to heat electrically, it does actually heat the space effectively.

I have been running my heater on red diiesel (gas oil) as this is available locally from a filling station pump, though the next fill will be paraffin from the supplier that Stevie GTR suggested. The unit was sold as 5Kw output and, while I have not accurately measured the fuel consumption, I suspect that it is probably nearer to 3Kw (5KW should be around 1/2 litre an hour, or 2 hours per litre – I supsect I am getting nearer 3 hours per litre) – typical Chinese performance exaggeration here.  Before the current cold snap I tended to turn the heater off after 3 or 4 hours as I was getting too warm – not had the inclination to go out to the garge at -2 C to see how it performs this morning !

As David A has pointed out, the documentation supplied with the Chinese heaters is, at best, poor I downloaded Webasto literature before I started installing mine and, as I said earlier, I had a couple of years using Webastos in Chausson motorhomes. The Chinese heater has actually proved to be more reliable than one of the two Webastos – the second unit failed the second time I tried to use it & had to go to a Webasto agent for repair under warranty.

Nigel B.

 

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