Chimney Problems

We have encountered another interesting problem – we try to treat all the problems we encounter on this build as interesting! –  and spent another unexpected few hours today, researching. This is with the wood stove or, more precisely, the flue / chimney for the wood stove. It could be a big problem, or it could be relatively easy to solve. We shall see.

The issue is this: We had assumed that we would be able to insulate the chimney where it exits the building with some kind of fire-resistant insulation material. However our installer says that the Ontario building code requires space around the chimney where it goes through each floor and the roof / insulation on the outside, and that there are no insulating products certified in Ontario with which one can fill this space. So, basically, we would create both a thermal bridge and a big hole in the envelope, all in one go. This would undermine the air tightness of the envelope and cause big problems for passive house certification. Both we and the installers are doing some more research but, as we see it now, we have 4 options:

1. Build a bigger masonry chimney through the house down to the first floor, which we can insulate.

Advantages:
Not many, apart from it being somewhat insulated and complying with code.

Problems:
i) More expensive
ii) This might be too big for the space we have – it would end up taking up more of the little corridor to the upstairs toilet and bathroom. We certainly can’t put 11″ of insulation on, as on the outside of the house. We have asked the installers whether we could do this just down to the attic floor level. They are getting back to us.

2. Install the stove next to an outside wall, and put the stove pipe directly out through the wall into an external flue / chimney.

From my research, this is also what happens most often in Europe.

Advantages:
i) Apparently the stove pipe can be sealed and be in direct contact with insulating materials, whereas the chimney can’t. I need to confirm this.
ii) No need to cut any more large holes in interior CLT, and much easier to deal with a pipe going through the wall than the roof

Problems:
i) If we just wanted a stove for heating the house, we could install the stove near to any outside wall we wanted. However as it’s a hydronic wood stove and mainly for water heating in winter, we have to install it fairly near to the tank system. If the stove needs to be very near to the tank, then we won’t be able to see it. That’s not ideal but not the end of the world. I will investigate how far the stove can be from the water tank to still work effectively etc..
ii) If we have to put the stove hidden in the utility space, then we will have to be very careful about exactly where it fits, in relation to the tank, outside chimney etc. We would also have to rejig water piping to accommodate the washing machine etc. (but which could even go in the pantry instead).

3. A more advanced technical solution that isn’t specified in the code

One such solution is made by the German company Schiedel,
http://www.schiedel.co.uk/products/ceramic-products-and-systems/chimney-systems
(this is the UK site, which is in English, but they only sell directly in Europe).
It is a masonry-based chimney an integrated design. Apparently this is also used in passive houses in Europe. One version of their chimney also includes and integrated air intake for stoves that need it – and I am still not 100% sure if we might need external air intake or not, opinions differ and we need to talk to the HRV supplier.

Problems:
i) Lack of certification. We would have to discuss any such route in consultation with our local planning officer, and probably have yet another engineer’s certification.
ii) More expense – including dealing with ports and import tariffs, overseas delivery etc.
iii) Time
iv) How insulated are these systems? We would also need to check the insulation rating etc.

4. Abandon the wood stove idea, ask for a refund and send the stove back.

Advantages:
i) Would save us all the problems of cutting holes in walls, inside and out, insulation issues, and everything else associated with the stove
ii) Would save us the costs of buying pipes and chimney, installation of all of these and stove.
ii) We can still use the rest of the water tank and solar thermal panel system.

Problems:
i) Some expense (and effort) to send stove back
ii) We would have to use electricity for the supplementary / winter water heating until we work out something better, perhaps even going back to the currently inefficient, but in the future perhaps more efficient, use of Solar PV-generated electric.
iii) Need for a heating solution that the township is happy with – perhaps simple underfloor water heating would be enough. We could also investigate ground-source heat-pumps again in more detail again – we had abandoned the idea on ground of practicality (with the bedrock so close to the surface here).
iv) The stove supplier might not accept a return. We need to check.

We are currently leaning towards 2. or 4. (in that order).

If we can perhaps install the stove on the west side of the lounge then 2. would actually be pretty great. We would also have more space in the utility room…

We are still unsure what other passive house designs in Canada have done and are waiting for some feedback from our advisors. Watch this space…

Heavy Duty

The delivery of our Wallnofer Walltherm stove, water tank and solar thermal panels had been delayed by bad weather along the route from PSES in Nova Scotia and we were not expecting them until Monday. However, we received just an hour’s notice at lunchtime today, that they would be arriving off the next ferry. It was barely enough time to get the back-hoe / fork-lift from Hulton’s…

But, having got the three pallets off the delivery truck, the difficult job of getting the very heavy water tank, and even heavier stove, into the house, began. One of the problems caused by the delay was that the doors had already been installed, meaning that clearance was limited. Luckily the water tank’s insulation is designed incredibly conveniently so it zipped off. The tank itself was still 190kg (420lbs), and big too but the four of us (Chris, Steve, Anne and David) managed to pass it over the sill of the tilt and slide door, which couldn’t take any weight as it is still not fully supported, and get it onto a flat trolley inside the house and then into the machine / utility space.

The stove was smaller but unbelievably even heavier. We partly disassembled it, removing doors and as many of the fire bricks as we could, but we probably did not reduce its 300kg (660lbs) by any more than 10%. To get it into the house and over the sill, Chris thought up an impromptu ramp and ‘bridge’. With two people pulling, two pushing and all of us watching the balance of the stove, we managed it…

Coming off the truck: 1. solar thermal panels

2. the wood stove

3. the hot water tank

Unzipping the tank insulation

Unwrapping the tank

This tank has nothing David can’t deal with!

Lift!

Hoist!

Anne is happy to get the tank inside

The water tank in situ

Just like Christmas! The stove box had lots of little packages inside…

Disassembling the stove to make it as light as possible

Stove parts ready for later reassembly

Building the ramp

Hold it…

… and heave!

Over the sill…

…and the stove is inside.

 

Everyone worked really hard today, but we aren’t finished this week. The weather doesn’t look great next week, so we have to work tomorrow to waterproof the house as much as possible for the Christmas and New Year break.

Heating a Passive House

In our last post, we mentioned two major design changes that we’ve made just before the point of no return. The first was the choice to go with a factory-cut wood fibreboard-clad CLT structure for the house.

The second was about heating. Now some people reading this, especially those planning a passive house themselves, might be thinking: “Heating? We don’t need no stinking heating!’ And, yes, we too had planned to have a house that essentially had no major heat source, that would be heated almost entirely by the passive solar gain and the warmth of bodies in the house, all of which would be kept inside by the air-tight envelope and incredibly efficient Energy Recovery Ventilator (ERV) – more about which in a later post.

However, something else came up: hot water.

I should mention that there are certain peculiarities with our site. Where we’re building the house, there is hardly any soil, literally inches, before you hit the limestone bedrock, and beyond, further down the slight slope where there is more soil, we have to install the septic field (there is no mains water or sewage on Wolfe Island). This means that ground source heat pumps etc. are not really a realistic option.

We were intending to use a combination of solar thermal water heating panels for three seasons of the year, supplemented in the winter by on-demand electric water heating batteries powered by a solar PV array. But the latter turns out to be very inefficient and expensive. There are systems that can supposedly heat water directly from solar PV panels (i.e. without inverting the power and storing it), but these are relatively new and we can’t find any working examples. And the other thing with all these complex PV-based systems is that they all need monitoring and the number of high-tech control panels etc. soon starts to get ridiculous. We’re far more interested in building a home for living in with appropriate technology, not a high-tech ‘smart’ home.

So, we’ve going back to basics and, as with the structure of the house, are looking to wood.

We’re going to have a wood stove. Yes. But not just any old wood stove, we’re going to install a Walltherm ‘natural down-draft hydronic wood gasification stove’ from Power Strength & Energy Solutions Ltd in Nova Scotia, (it’s actually made by Italian/ German company, Wallnofer). This not only burns wood, but also burns the gas that is generated from burning the wood, in a secondary chamber. What’s more, although it still looks pretty smart and you get the wonderful visual warmth that only a fire can provide, it is designed primarily to heat water. The stove has a water heating jacket, which in normal use takes 70% of the heat generated. For small, highly insulated and passive houses like ours, which don’t need much in the way of ambient air heating, there is also an extra insulating jacket that redirects even more of the ambient heat to the water pipes.

Walltherm Wallnofer hydronic wood stove

Even better, the suppliers of the Walltherm also sell a multi-source water tank that also takes solar thermal energy, as well as the roof panels etc to go with this (PDF). We probably won’t need to use the Walltherm itself for much more than an hour or two a day to generate all the water we need, so we’ll use relatively little wood, but this will also mean that the house will be nicely warm and not just tolerably warm, in winter. If we end up with too much hot water, we can probably send some of the water heated in a simple pipe out around the edge of the downstairs concrete floor – a simple version of underfloor heating – as well as having more baths, of course.

Full Wallnofer System

The obvious question is why not a hydronic pellet stove? Pellet stoves are highly efficient, produce very little waste and pollution and use up waste sawdust. What’s not to like? Well, we have a pellet stove as the only heating in our current house, and to be honest, we haven’t been impressed for several reasons:

1. They require electricity to operate. Both the ignition and the auger that supplies pellets to the firebox are electrically operated. With the relative frequency of power cuts here, this has been an issue, and while it won’t be in our new house with the PV-supplied battery system, it does make the system less resilient than a wood stove, which can operate without electrical power.
2. No-one delivers pellets to Wolfe Island, however it is easy to have wood delivered. What this means is that we have to drive to suppliers to collect ten bags at a time every week for about four months before winter. It’s just inconvenient and inefficient.
3. The pellets come in plastic bags, which is unnecessary waste and, whatever is said about local production, in practice most of the pellets seem to be trucked in from the USA.
4. Our pellet stove just doesn’t seem to produce a very high level of heat, whatever its nominal rating, which means we’re using a lot of bags of pellets in winter, and it just doesn’t feel as comforting as the wood stoves in friends’ houses.
5. Last, the Walltherm’s two-stage burn makes it almost as efficient as a pellet stove. In fact, we’ve decided we will probably sell on our existing wood stove and replace it with a small wood stove in our current house (which will be converted into a studio and guest space).