Wood burning stove
The Living Building Challenge (LBC) is strongly against integrating any form of combustion in a compliant house design: no fireplace, no pellet stove, nothing that burns, full stop! Net zero energy goals should be attained via renewable sources, like solar or wind energy.
The main exception allowed applies to a very specific scenario:
In the limited instances where development is allowed in Living Transects L1 and L2 as defined in Imperative 01: Limits to Growth, it is acceptable to install a single wood stove or fireplace because ecological impacts are minimal, intensely local fuel supply is guaranteed and there is a strong cultural legacy of the “hearth in the wilderness” that contributes to the feeling of hygge in locations where humanity is not otherwise present. ( Hygge is a Danish term that is difficult to translate but implies a sense of warmth, coziness, well-being and belonging in a certain place. )
While I fully subscribe to the goal of reaching a net zero energy balance and avoiding heating devices that burn any type of fuel, I’m in agreement with Frank Lloyd Wright’s often quoted statement that “the hearth is the psychological center of the home”.
Medellin’s temperate climate all but eliminates the need for a fireplace as a domestic heating solution, except for a handful of days in a year. However, the irrational need to congregate around a fire seems to be wired into our brains. My fondest childhood memories are linked to wonderful chats and entertaining board game sessions we had in front of the fireplace.
Early in the design phase of the project we fell madly in love with a stunning piece of fire-art, the Gyrofocus. We wanted to make it the central piece of the house, the star around which our lives would orbit.
However, we quickly realized that this dream was fraught with practical issues:
- Weighing over 300 kg with the flue system, the Gyrofocus absolutely requires an adequate supporting roof structure, more readily found in steel/concrete houses than our planned glulam/plywood minimalist Japanese ceiling.
- The quotation from the Focus distributor in Colombia showed a stratospheric price of COP $41M, unaligned with our budget.
Even worst, since our aim is to build an essentially passive house, the heat radiated and convected from a fireplace or stove can quickly exceed the heating demand of the living room, even though it has an open floor plan. In consequence, the heating power of the fireplace or stove needs to be low (i.e. 1–3 kW).
The LEED v4 Reference Guide for Homes lists some prerequisites in the Indoor Environmental Quality chapter, Combustion Venting section, namely as part of Compliance Path 1:
Select a fireplace with a permanent solid glass enclosure and ducted outside combustion air.
Compared to LEED for Homes 2008, this is a new prerequisite based on EQ 2 Combustion Venting. The Green Rater team will conduct an on-site verification to ensure compliance.
Some wood burning stoves are designed to draw the combustion air from outside; in this way, the stove does not use indoor air, hence there’s no risk to compromise indoor air quality, particularly in well-sealed passive homes, as well as reducing backdrafting.
For an extra LEED point, one can install a wood burning stove that is EPA certified:
For any wood- or pellet-burning stoves, install equipment that is EPA certified. For wood-burning fireplaces, install equipment that is EPA qualified. Provide power or direct venting.
There’s a dizzying array of wood burning stoves that meet or exceed the EPA requirements, a few small enough and with a modern aesthetic that would fit perfectly in our project, such as:
The Stuv 30 Compact has received a glowing review from the owners of a sustainable house in France. With a heating power of 3 to 9 kW it is suitable for installation in a passive home. As an added bonus, it can rotate 360 degrees, like a Gyrofocus, and is ideal for being located as the focal point of both the living room and the dining room.
We’re thinking of importing the Stuv 30 Compact wood stove from Europe or the US since the brand has no distributor in Colombia. We would contract a qualified installer to take care of the flue and the roof flashing. Other matters that are still unresolved are:
- Can we find a double-walled flue locally? Where?
- Can the flue be powder-coated the same color as the stove for a better and more durable appearance?
- Where are we going to store our cordwood away from the rain? Stuv recommends that the degree of humidity of the logs should be less than 20%.
- The length of the logs is limited to 40 cm when positioned vertically. I suspect this means I’ll end up buying a chainsaw!
- The stove only weighs 114 kg. Nevertheless, we need to mention that to the structural engineers and make sure the floor can support that weight.
Equally interesting is the question whether or not we need an open fireplace on the terrace, but this is a different topic for a later post.
Originally published at casaleed.org on February 15, 2014