It was taken during the build when we had blue skies and sunshine and someone on site tall enough to open the roof windows (not me, they are so high up I get vertigo if I try).
Being a bit new to this malarkey, and a bit chary about massive energy bills, we've been monitoring our energy usage fairly closely since we moved in and we're beginning to get a bit of a feel for how our consumption is going.
Now if you are an expert in all things green this will be like grandmothers and eggs to you so just feel smug/exasperated at my idiocy and move on but, just in case you're not, here's what we've learned so far:
- We have a generator meter that shows what we're generating
- You don't need sunshine to generate electricity, just daylight because it's the sun's energy that makes the panels work
- Having said that, around mid-winter when the sun is lowest in the sky our panels only generated electricity on days when the sun actually shone on them
- Now the sun is higher in the sky, and the days are a bit longer, we can generate some energy even when the sun doesn't shine
- And it doesn't shine very much in this bit of the West Midlands in winter so that's fortunate
- I wish I'd been taught more physics but this site is useful for novices
By monitoring our energy usage and keeping a record of the external temperatures and amount of sunshine we've ended up discovering the obvious* about energy usage in the house. On sunny days the sun through the large south facing windows means that the rooms get warmer, we use less extra heating and we generate electricity so our overall consumption is lower. On grey days the opposite happens.
Normally there's a 1 degree difference in the temperature as you go up through the house so the ground floor is on 18, the middle 19 and the top 20 but the weather this house likes least is grey windy days as this reduces the temperature on the top floor of the house. I'm not sure if that's supposed to happen but, at the moment, it looks like it does.
The house has been designed to run at 20 degrees but as the thermostat is on the ground floor 20 degrees at the thermostat means 22 degrees on the top floor and we are finding that's far too hot for bedrooms. There was much discussion at the end of the build about the location of the thermostat as it's just by the front door and therefore subject to blasts of air from the porch when the door opens. It was suggested that it should be moved to the middle floor where temperatures are more constant and on reflection that should have happened but the discussion was just before we moved in so the thermostat hasn't moved. I'm not sure if the house will keep its temperature differentials once the fabric has warmed up and I'd be interested to know how (ie: in what direction) the house warms up so I will have to ask one of our expert visitors when they come.
As you see, the key thing about this house is that you need to work with it as it's very much an organic entity. This is not a normal way to have to consider your house is it? I refer you to the Ultrahouse in The Simpsons. Anyway, I'm finally understanding how the ventilation system works and if you look back to the previous post with the little Saturns sticking out of the walls you'll see how the warm air enters the rooms. What I forgot to write was that it exits the rooms under the doors where there is a 5mm gap** and this is balanced out by the angle and opening of the Saturn so the air doesn't enter or leave too quickly or hang around too long. Overall it takes just over two hours for the house to change its air so the air quality is excellent. The final thing to note is that if you want to keep a room warm then you keep the door closed because the northern corridor doesn't have any vents, which means that if your door has a bigger than 5mm gap (on account of being open) all the warm air rushes out into the chilly corridor rather than reaching you as you sit at your laptop....
... so I'll get up and sort that then!
* It may be obvious, but it's a lot better than being surprised by the data
**As a tetchy aside I would like to point out that 5mm seems to also be the diameter of a vacuum cleaner cable so I spend a considerable amount of time extracting the latter from under doors when cleaning, but expect the house will train me eventually.