No Jotul woodburning stove or fireplace insert can function properly without a good chimney. Think of the chimney as the engine that drives the Jotul wood heating system. Think of its fuel as heat. Think of the power it puts out as draft. The more fuel (heat) you give this engine (chimney), the more power (draft) it will deliver.
No woodburning stove, fireplace or furnace can function properly without a good chimney. A good chimney is:
A good chimney and system design produces desirable performance characteristics:
When planning a woodburning system, the first thing you need is reliable advice on matching the appliance to the right type and size of chimney. Most wood heat retailers and chimney sweeps can guide you and there may be government agencies and publications you could get locally. We strongly recommend having your chimney professionally installed by someone whose references you have checked. You never want to lie awake at night wondering if an incompetent chimney installation is putting your house and family at risk.
(hint: it's really the chimney that's doing the performing!)
Think of the chimney as the engine that drives the wood heating system. Think of its fuel as heat. Think of the power it puts out as draft. The more fuel (heat) you give this engine (chimney), the more power (draft) it will deliver. So, the hotter the exhaust gases, the more draft is produced. Draft, by the way, is good. It's the suction that keeps the smoke from coming into the room. Insulation in the chimney is important because it helps to keep the exhaust hot until it is expelled outside, and so, increases draft.
The chimney works with the stove or fireplace in a kind of feedback loop. Heat in the chimney makes draft, which pulls in more combustion air, which makes the fire burn hotter, which delivers more heat to the chimney which makes more draft and so on. An insulated chimney makes more draft with less heat.
Wood-fired stoves and fireplaces operate on natural draft, meaning that no fans assist the flow of exhaust. For the chimney to function correctly, it needs to receive about twenty percent of the heat energy produced by the burning wood. Past experience has shown that when wood stove efficiency is much over 80 per cent, water vapor condensation can begin to occur in chimneys, especially outside ones made of masonry. Never starve your chimney of heat. It needs heat to function properly.
In winter, a well-designed and properly installed chimney makes some draft and flows some air upwards, even when no fire is burning. When you build a fire in a stove connected to such a chimney, the kindling ignites easily, draft increases rapidly and you have a nice bright, hot fire right away—and no smoking. This is the kind of system you want in your house.
Straight systems produce some upward flow, even when no fire burns. When it is cold outside, the warm air inside the house wants to rise, producing a pressure difference: low pressure low in the house and high pressure high in the house.
The pressure difference is called stack effect, and between the positive and negative pressure zones, is the neutral pressure plane, at which the pressure in the house equals atmospheric pressure outdoors. The colder it is outside, the greater is the temperature difference, so the stronger is the stack effect. A chimney installed in the middle of a house naturally overcomes stack effect by being as warm, but taller than the house.
Houses are being built more tightly sealed for increased comfort and lower energy costs. This is done by using doors and windows with gaskets and walls with a continuous air barrier (usually plastic film). If you turned on a powerful range hood or downdraft kitchen exhaust in a relatively small, tightly sealed house, it might suck so much air out of the house that the pressure inside would fall enough to overcome chimney draft and suck the smoke out of the stove. It's not that common yet, but it can happen.
1. Put the chimney inside the warm building environment
2. Go straight up, no elbows or offsets
3. Insulation around the flue liner
4. Flue sized to match stove
If you live in an area that has a real winter – the ground freezes and you get some snow – or if you live at high altitude – say more than 4,000 feet – you'll need to follow these design guidelines exactly in order to get perfect performance. You people at low altitude with mild winters may not need to be quite so fussy, but, then again, good design always pays off in better performance.
