The Tiny Cottage’s First Fire
“Fire!” Yelled Holly with glee! Finally we had heat in our tiny cottage. Two weeks ago to be exact since the lighting of our first wood fire. Ben promptly wanted to cook pancakes. It’s been a long time getting to this point and I wasn’t sure if we were going to have the wood stove installed before the winter was over. Fortunately the cottage keeps itself reasonably warm even in our winter.
Pipe Penetration Parts
To light a fire first we need a wood stove. Check! We got a cute little Vogelzang Boxwood Wood Stove last December 2006. Then we needed to seal the cottage up tight. Check – walls up, roof on, windows in, door done. Next I opened the chimney hole I had left in the top of thenorth wall over the corbel. That was breezy as the warm cottage air rushed out into the winter sky. To stop the flow of air, hold the pipes stead and provide a back form for the lightweight insulating concrete as we packed the space around the pipes – thus the pretty piece of 2″ thick pink foam with holes cut out above.
Filling Vent Pipes
In addition to the chimney penetration there are a number of vent pipes that pass through this area to provide ventilation for the drain waste system, the kitchen and the bathroom as well as a conduit for future communications wiring if I need it. I wanted as many penetrations to be in the same place as possible. Many of them are ventilation related so rising in a chimney stack together works well. I went with a wall penetration for the chimney and vent pipes as it is easier to prevent leaks that way. I would rather not have water running down from the roof into the house. It is possible that I’ll put up a communications relay and the chimney will be our highest point so that also fits well there.
Before placing these penetration pipes I filled their ends with a bit of foam so we won’t be constantly losing heat. Some of them, most(?), won’t be used for a long time but need to be there when I’m ready so I don’t have to drill through the wall like we did in the kitchen.
Chimney Pipe Sealed
Since it would take time for the insulating concrete to cure before I will want to lite the stove we also sealed up the penetrating stove pipe. This is a 8″ (~10″ outside diameter) fire clay pipe which protects the insulating concrete from the heat of the wood stove chimney. The insulating concrete protects the house structural concrete and the PVC vent and conduit pipes from the heat. A smaller diameter pipe passes through the larger diameter pipe.
To make the insulating concrete we substituted vermiculite for sand using four gallons of vermiculite rather than three gallons of sand – this was by volume rather than weight. This created a mix that was 8:2:1 (Vermiculite:PortlandCement:Water) by volume. The goal is to create a lightweight insulative concrete that provides for thermal expansion and keeps the heat of a hot chimney away from the vent pipes and structural concrete of the house which could be damaged by excessive heat.
I find it is better to hand mix the vermiculite concrete than to use the mortar mixer which tended to break down the soft vermiculite making a medium density concrete.
What is Vermiculite?
Vermiculite is a natural mineral that expands with the application of heat. The expansion process is called exfoliation and it is routinely accomplished in purpose-designed commercial furnaces. Vermiculite is formed by hydration of certain basaltic minerals.
In other words, popped rocks!
With Holly’s help on the outside we braced the pink foam form in place and foamed it along the edges to get an initial seal around the form. After setting the pipes in their respective holes I packed an outer layer of medium density concrete to stop mice and then the insulative concrete as tightly as I could, filling the cracks and crevices around the pipes. The insulative concrete is an interesting material – it feels very spongy when uncured.
Is Vermiculite Safe?
There is some concern with some older vermiculite products about asbestos. From what I’ve read this is not an issue with newer vermiculite. However, it’s dusty stuff so don’t breath it. Same as with portland cement, toner or any other fine dust. Once it is bonded into the concrete matrix I have no concern about it being a health risk. Our granite with its out-gassing of radon is probably more dangerous. The solution to pollution is dilution. e.g., Ventilate!
Pipes Placed in North Wall Penetration
Once the smaller spaces around the vent pipes were packed we placed the chimney fire clay pipe and packed more insulative concrete around that to separate it from the vent pipes. The reason for doing this in two stages was to better be able to fill the small crevices between the pipes. A packing rod is very helpful.
I wanted the plastic pipes well insulated from the potentially hot chimney thus the double walled chimney, the fire clay and the insulative low density vermiculite concrete spacing the PVC pipes away from the chimney penetration. Should the PVC ever get warm and outgass the system is setup so the gasses exit the house – these are vent pipes. I don’t want fumes coming into our breathing and living space. So far the PVC pipes have all been cold to the touch so it is working.
Will Burning the Stove
While the ch
imney penetration cured we took the woodstove outside and burned it. When you buy a stove or pipe they come coated with grease. The grease stinks and I suspect it is not good to breath the fumes. So we set the stove up outdoors and burned a fire in it for a full day to degrease it. In addition to burning off the stove we also did each of the sections of stove pipe and the elbows. I’m very glad we did this because it stank to high heaven! I would not want those fumes indoors.
Fumes off Stove Pipe
Here’s a photo showing the grease fumes burning off the stove pipe outdoors. The made the most interesting smoke rings rising up the pipe.
Hope Tending the Fire
Having a wood stove burning outdoors is a prime time to satisfy the urges of those little pyromaniacs in your life, er, I mean to teach your kids about how to tend a wood fire… Yes, that was what I meant!
Stove Pipe Screw
To make sure that stove pipe sections don’t come apart in use I drill small holes and screw the sections together. I learned to do this back in the old farm house down the hill where there is a long horizontal section that tended to sag – well worth the effort. By the way, self-taping screws don’t. Looking at them I doubted it but the hardware store guy insisted they did. Pre-drill all holes at 1/2 the shank thickness.
Stove Pipe outside
A view looking from the north side at the stove pipe exiting the top of the north wall of the tiny cottage. The pink foam form is still in place in this photo and it isn’t quite done at the time this photo was taken – e.g., the foil flap. The stove pipe is wired to the wall via bolts set in the concrete. There is fireproof fiberglass packed on the inside and the outside of the fire clay pipe around the metal pipe to provide thermal expansion and stop air leaks around the pipe.
Some interesting details:
1) We have about 18′ of stove pipe inside the house to extract the heat from the fire before it exits the chimney.
2) The total chimney height is only about 12′ of vertical head but it drafts very well, much better than the 30′ chimney on our old house ever did. This makes it easier to start fires and we don’t get back drafting and smoking – something I was concerned about with such a short stack since we had trouble in the farm house with this. This draft also serves to draw in fresh air through the floor pipes. Eventually that will work to power the air circulation system and the earth air pipes we’ll install next year like I had put in the old farm house which worked so well. Fresh air, especially in the winter, is important.
3) The metal stove pipe is hot but touchable where it exits the fire clay pipe in the north wall penetration but cool by the time it gets to the elbow however we’re not getting any condensation or creasote inside the pipe. That’s good news. It means the stove is running effiently and not wasting much heat to the environment. One improvement I plan to do is change the final elbow to a T so I can have a cleanout. That’s why I built the corbel down below the chimney. I’ll also put fire clay pipe up the exterior and do masonry around it to insulate it and further improve the efficiency of the draft. A project for another day.
4) The wires that hold the stove pipe in place sing with the wind. It is faint. When I am inside the house it sounds like I’m hearing distant cathedral bells. Quite pretty. It took me a while to figure out what was making the sound as it only happens when the wind is right – very often in the evenings and late afternoon. The wires are attached to anchor bolts that are embedded in the concrete of the roof which acts as a sound board. It gives me ideas…
Chief Chef Ben Cooks First
Ben got to be the first person to cook on the new woodstove. He wanted to make pancakes for breakfast. Delicious!
Ben experimented with cooking the pancakes both in the skillet and directly on the woodstove top. The seasoned skillet is easier to flip from. I’m going to look into a flat griddle top as that may be more useful for our cooking needs most of the time. Anyone know of a source? I may endup having to make it as this stove is a bit of an unusual size.
Stove Coals & Wood
We’re able to easily build up a very nice bed of coals in the stove. This surprised me. I am used to our old Sam Daniels wood stove which is literally big enough for me to climb into – I’ve done so on occasion to patch and repair it. I had not expected the Vogelzang to hold a fire overnight – it’s not air tight – yet it does. This photo doesn’t quite do the stove justice – the entire bed of coals was glowing gently right then as I had added new wood for the evening.
The wood stove is inside a shroud of masonry which is thermal mass to soak up the heat of the fire. I did a lot of experimenting in the old farm house with adding thermal mass to our Sam Daniel’s wood furnace. It makes a big difference in how well a stove performs. Eventually my goal is to build a masonry stove on this base which will have ovens, larger cook surface, a smoking changer and be even more efficient.
Under the woodstove we put sand and bricks to protect the concrete pad from the stove. We also put sandin the bottom of the stove to protect the bottom plate of cast iron from the heat of the coals. In restrospect I think that might have been overkill as there is a nice bed of ash. But, it makes me more assured the bottom won’t crack.
Tuesday of last week we cut firewood, just two trees worth from the log pile that has been drying for a year. Will is to the point where he can lift and hold the chainsaw straight out from his shoulder at arms length – my measure of when one is ready to learn to use the big saw. He got his first lessons in blocking up wood. A milestone.
Night Hawk CO Monitor
Call me Nervous Nellie but I wasn’t comfortable until we had something up to make sure the stove wasn’t going to poison us. Smoke, Fire, Carbon Monoxide be gone. We’ve been running the woodstove for two weeks now and the CO monitor has read a steady zero.
Something that always bothered me about our old farm house is it is a neatly stacked bonfire ready and waiting to burn. Our new tiny cottage is made of concrete, granite, marble, glass, steel and aluminum – not very flammable. Even the contents aren’t likely to make much of a fire – We have very little possessions there, they
are stowed in trunks and they aren’t near the fire. It feels a lot safer not sleeping in a funeral pyre!
Outdoors: 9°F/1°F Sunny
Farm House: 57°F/47°F
Tiny Cottage: 58°F/49°F