To heat our home in winter we wanted to explore a few methods. One of them was installing a wood furnace that heats up the space while you are cooking on the top or using the oven. We spent a lot of time searching for the perfect wood furnace: We wanted it to be compact and not to strong, so our house doesn’t overheat; we also really wanted a cooking top and oven so we can use the heat from the fire as efficient as possible. We also wanted the stove to have a lot of mass so it could store the heat and evenly release it throughout the day, instead of quickly heating the space but also cooling down after just an hour.
We first added another ESB board to the floor where the stove would be installed. On top of this we screwed a sheet of stainless steel. This elevation helps to distribute the weight but it also makes sure that this floor piece has the same height as the wooden floor boards that will be installed later. We then screwed thin wooden beams onto the floor as a guide for our aerated concrete blocks. This type of brick is very light in weight (9kg/brick) but still able to carry a lot of weight. We used special mortar to glue two layers of bricks (15x20x60cm) together in a U-shape.
We found some enormous clay fired bricks second hand that had the perfect dimensions to surround our wood stove. First we placed a large brick onto the U-shaped bricks that will support the wood stove and collect the heat that radiates from the bottom of the stove. It was quite heavy (+-80 kg). To lift it without damaging the brittle aerated concrete blocks we slowly lifted it using wooden planks.
Then we put the wood stove in the right spot, leaving some room on the sides and in the back for more fire clayed bricks. Next we temporarily installed the first pieces of flue pipe to mark out where the hole through the wall should go. The seize of the hole is equal to the size of the insulated flue pipe plus another 3,5 cm extra on all sides (which is equal to the thickness of the insulated wall shield that will surround the insulated flue pipe). We cut through the ESB with a jigsaw to make the first hole.
When both holes were made we pushed our insulated wall shield through the wall. We made this ourselves using a 1.5 mm stainless steel sheet for the outer ring , 4.5 mm mineral wool for inside and a 1 mm aluminium sheet for the inner ring. Once we placed this piece through the hole we marked where it was touching the ESB walls (inside) and the Gutex boards (outside) so we could cut these pieces away using an angle grinder. We then cut two stainless steel sheets with an oval hole inside of them which were used to make this installation air tight.
We first put heat resistant glue on the stainless steel sheet that was installed on the inside after screwing it tight against the wall. Next we used high-temperature aluminum tape to seal up the gaps between the insulated wall pipe and the steel sheet. We then did the same for the outside, but instead of using glue between the sheet and the Gutex we decided to screw the stainless steel sheet against the Gutex and seal the edges with Tescon Vana tape afterwards.
We then cut a slightly bigger hole in the aluminium heat shield. We then placed the 45° insulated flue pipe throught the aluminium, inside the insulated wall shield. Below the 45° pipe we attached an insulated 45° angle piece, followed by a transition piece that connects the insulated corner piece with an uninsulated flue pipe, which is connected to the wood stove below.
After months of research we ended up choosing the Josef Davidssons JD27. This 4.5 kW stove is still quite strong for our 40m3 home but this type of stove is often built into Swedish kitchens, surrounded with bricks that can capture a lot of the heat and slowly release it hours after the fire is out.
Behind the bricks we installed an aluminium sheet against the ESB that is spaced 2cm from the wall. This will act as a heat shield to protect the wall behind it. The sheet is fixed on the left and right with thin wooden beams and left open on the top and bottom (here it is elevated 2-3 cm from the floor) so air can flow behind the sheet through convection.
This type of wood stove has an outdoor air connection on the bottom back left corner. Since our home is very airtight it is recommended to add exterior air into the woodstove to minimize draft and improve air quality. To install this we first had to drill a hole into the clay fired brick.
Next we measured a 45° angle from the top and bottom of this hole towards the Gutex boards behind it. Here we marked and cut out the second hole which is slightly higher then the first. We chose to use a double 45° angle in our flue pipes because it improves the draft and reduces soot and creosote buildup compared to a single 90° bend because it keeps the flue gases moving more smoothly and hotter.
On the outside, a 45° corner T-piece with dust collection is connected to the 45° flue pipe, followed by 1.5 metres of insulated flue pipe. On top a chimney cap with spark arrestor is installed.
