Heating greenhouse & garage
I’m just wondering where to start in replying to your Email so I’m going to start with the actual heater.
Electric greenhouse heaters are more efficient, cleaner, safer, quieter and practically maintenance free to run. Normal gas, propane and paraffin heaters often do not attain complete combustion which can lead to a build-up of carbon monoxide, they do not pump CO2 into your greenhouse and are generally less efficient to run. For this reason we no longer sell gas heaters. This season we are stocking the Slimline Eco Heater with a new built in thermostat, I would definitely recommend this model both for your greenhouse and for your integral garage. It is designed for running over a long period of time and due to the automatic heat sensitive cut-out and built-in thermostat, they won't guzzle your wattage and are perfectly safe to leave on. The heater is available in three different sizes 0.5m, 1m & 1.5m – the supplier recommends that you buy the biggest heater you can fit in the space just as you would in a room in your house. So in your case the 1.5m would prove to be the most suitable.
Calculating the running costs of these heaters is also relatively straightforward; just check the power rating (either 0.5 = 55W, 1m = 120W & 1.5m = 190W) and then compare this to hourly rate per kw (kilowatts) you are charged by your electricity provider on one of your electricity bills and you should get a fairly good idea what running them will cost you. The link above will give you more information on the Slimline Eco Heaters.
You have certainly done all you can in reducing heat loss in your greenhouse. In reply to your question about double bubble wrapping your greenhouse, if you have used standard packing bubble wrapping I would say no to double wrapping because you would probably cut down on light but if you have used the Harrod supplied standard Bubble Insulation this is UV stablised and is tri laminated, we now offer top quality 20mm large double laminated bubble insulation which offers even better light transmission.
With regards to your integral garage I would be a bit concerned with the light levels in there. Obviously you could stand your olive and citrus trees close to the window. Citrus trees should overwinter in a south facing window, conservatory or greenhouse. Your lilies and cannas would not have a problem with darker conditions as they are bulbs/rhizomes so maybe you should be a bit choosy as to what you put where. You could also increase the light in the garage during the day (12 hours) by installing a Grow Light Kit – this will replace low levels of winter light or let you grow in places devoid of sunlight with a combination of powerful 200W low-energy horticultural lamps and metal reflectors allowing plants to germinate and grow with impressive results. Bubble wrapping your garage door would be an excellent idea. You could also curtain off a section using bubble wrap and keep this area warmer with the slim line eco-heater rather than trying to heat the whole garage. This would obviously need to be set up near the window for the best light levels possible.
You may want to get a Min/Max Thermometer for your greenhouse and your garage, these are good at telling you how cold the temperature reaches in the winter and how hot it gets in the summer.
I hope this has helped you but if we can help you further please do not hesitate to contact me or Customer Services for further information (Customer Services 0333 400 6400 (local rate)).
Lynn Burton - Horticultural Adviser