Getting the Most from Wood Heat - Better Heat Distribution

All the wood we use for heating our house, cooking our food and heating washing water is free. We collect and then break down untreated pallet wood from various local enterprises. However, even though we do not pay for this fuel, we still want to get the best from it and last year I built a stone 'storage heater' to give us a longer and more efficient heating period in our sitting room (link below). This year I turned my attention to the kitchen and the bedroom above it.

Introduction

We do all our cooking with a wood-burning cooker and this also heats the kitchen. The problem is that the heat is never distributed evenly throughout the room. This post describes how I finally started to think laterally and moved the heat likewise.

The Problem in Detail

The living quarters of our longère comprise four rooms each of about 27m² or 290 ft² the two downstairs rooms are heated by the cooker in the kitchen and a wood-burning stove in the sitting room.

In the kitchen the cooker is positioned next to a large chimney breast about a quarter of the way down the eastern wall of the room. Normally, the convective heat from a cooker would rise and 'mushroom' out once it reaches the ceiling and thereon be displaced by the rising heat to circulate around the room. In our case, the floor joists of the bedroom above obstruct the convection currents. These joists are 22.5 cm (9") deep and run from the north to the south walls (the long axis) of the room. Hence the convection currents from the cooker become trapped between the wall and the first joist and move toward the north and south walls away from the more frequented central portion of the kitchen. For most of the year, the heat output from the cooker is adequate to keep the kitchen 'comfortable' but I did want to boost the heat during the colder winter period. In the Winter Sue and I can end up huddled around the wood-burning cooker, in much the same way as used to happen in the sitting room before I designed and made the stone storage heater. As a bonus any additional heat would be directed upstairs and into the bedroom.

Using my trusty whiteboard aka the cover for our bicycle washing machine, I've sketched the layout of the problem, showing the heat trapped between the joists.

The Solution

In December 2016 I came across a promotion on Amazon for stove fans and I quickly realised that this was a solution to the problem, namely, breaking the convection cell created by the presence of the floor joists. I'd not seen these before so I read about. Briefly they are small electrically driven fans that are powered by the heat from the hot plate. The electric current comes from what is known as the Seebeck effect, a thermoelectric effect. I had to hand a domestic fan larger than those used for stove fans but I thought I would try the idea out using it. A few minutes in the workshop with some scrap timber and I'd made a floor stand high enough to bring the fan level with the cooker top. I positioned the fan at the rear of the cooker (photo below) so as to blow air across the hotplate surface and lit the fire. When the cooker was up to temperature the fan was turned on. Within minutes the results were felt around the room, the whole kitchen was warmer even at points furthest from the cooker. Even better, after about 30 minutes the heat could be felt upstairs in our main bedroom.

Without doubt the simple act of moving the hot air horizontally into the kitchen has changed the feel of the entire house. In fact, this blog post was written at the kitchen table and I felt extremely comfortable and warm the whole time!
 

The Next Step 

This is to reduce to a minimum the power required to drive the fan, maybe changing the fan to a smaller size, possibly one from a computer. All I know at the moment is that everything is much hotter and Sue has found that the setup also acts as fantastic hair drier!

..and now if you'd like to, sit back and watch the film:

All the best and thanks for dropping by. Please feel free to share this article, comment and/or ask for further information.

Until next time!

Cheers, Andy
© Andy Colley 2017

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