2 years on

Two years on, and we’re right in the middle of a record breaking heatwave. Tarmac on the roads is bubbling, trains are cancelled and people & animals are seeking refuge where they can. We feel very lucky that our home can provide that refuge. Over the last few days, when outside temperatures peaked at 29C, the house remained comfortably below 23.5C. It’s difficult to describe the feeling of walking in from the sweltering heat, but it’s just lovely. So how is this achieved? Most of the windows are externally shaded, so solar gains are really minimal. We’re keeping on top of night time purging and shutting the windows when the ouside temperatures rise above the internal. I appreciate the night time purge strategy only works when outside temperatures get sufficienly cool – it may well be that in future we won’t be able to rely on this and some form of active cooling may be needed – but hopefully not for some time. The consolation is that energy demand for active cooling would also be very minimal (similar to the very low heating demand in winter).

We opened the house up at the end of June as part of International Passivhaus Open Days and were delighted to welcome around 20 visitors, who were keen to learn about low energy building and experience the summer comfort.  The weather ‘played ball’, it was a hot sunny day outside but the house stayed nice & comfy inside despite the extra 20 bodies 🙂

In other news, I finally picked up courage and converted the shipping container left over from the house build into a workshop. Insulated on the outside and clad with locally sourced larch, it should hopefully blend in well with the landscape, especially once the wildflower meadow grows on the flat roof.

I have become more involved with Ecococon straw panel system as their UK technical support. If you have a project and are thinking of using Ecococon or have any questions, ping me.

Finally, look out for the dates for Passivhaus Open Days in November – we’re likely to open the doors again.

Summer comfort

With the recent heat wave in UK, it’s been interesting to experience internal comfort in our house. Although we haven’t fully moved in yet, we’ve been spending considerable time inside doing various finishing tasks. Over the last few days the external daytime temperatures have been gradually rising, peaking at a scorching 30 degrees C today. Night time external temperatures have also been going up, last night levelling at 17.5 degrees C. This pattern is likely to carry on over the next few days.

We’re really impressed with how our house has been coping with the hot weather. Internal temperatures have been fairly steady, gradually rising from 18.5 to 21.5 degrees C. We’ve been keeping the windows & doors shut and the ventilation unit on. The MVHR unit has a built-in automatic summer bypass, which kicks in at 21 degrees C. We can contribute the comfortable internal temperatures to a number of design features:

1. exposed concrete slab with its high thermal mass acting as a giant temperature regulator (warning: this can work both ways!)
2. 1.5m roof overhang along the south verandah means no direct sun hits the big glass = zero unwanted heat gains
3. external roller blinds to main bedroom (south facing), and two windows to east & west gables
4. high levels of insulation & airtightness in walls & roof (thermos flask effect in reverse)
5. fully vented facades & roofing. It is worth noting the facades and roofing are black colour, but the vented cavities help isolate the hot surfaces from the thermal envelope, slowing the heat flux down

We don’t have the hot water system installed yet and have not been cooking/ living in the house, so internal heat gains have been minimal (bar the dehumidifier which we’ve temporarily turned off). We’ll keep an eye on the temperatures & relative humidity and will start proper monitoring once we get connected to broadband. The initial impressions are very positive though and we can’t wait to move in!