Passivhaus

Last week I went on an AECB CarbonLite course on understanding the Passivhaus standard, principles and methodologies.

It was a really good day for learning what the standard means and getting an introduction to the software. It's encouraging that there is also a standard for renovation, not just for new build. It's great that it's possible to build new houses to a high standard of insulation and airtightness with proper ventilation that will use 75% less energy for heating than a conventional new build. However, we can't build new houses quickly enough to replace all our existing houses and we probably wouldn't want to. Therefore, if we are to have comfortable homes that don't cost a fortune to run then it's important to renovate our existing housing stock to a high standard, so that they are warm, properly ventilated and with good air quality.

One issue I have is that all the emphasis is on the use of energy post-construction/renovation to heat the house; the embodied energy in the materials used is not considered. This is something that must assume more importance in future so that there is a reduced energy demand to produce construction materials and build houses.

This week I've been up to York for a meeting of a working group called Renewable Building TWG. A summary of the meeting will appear on the group's page.

The group exists to facilitate the development of the renewable building products supply chain in the UK and members come from agriculture; or are suppliers, distributors or manufacturers of renewable building products; or designers and builders; as well as Government and researchers from academia, SMEs and large companies.

Since the group formed, some members were involved in a demonstration project, 'The Renewable House', built at BRE Innovation Park, Watford (pictured here). The house used renewable materials to deliver a low cost, affordable house that meets Level 4 of the Code for Sustainable Homes through materials. Group members have also been involved in other projects such as the strawbale houses at Waddington referred to in my April blog. Other members of the group manufacture and supply products based on renewable materials such as sheep wool or hemp insulation, wood fibre boards and others.

How does your garden fare?

We have had some prolonged dry spells this year already, in central and southern England in particular. So how do you cope with dry spells in your garden?

In our own garden we try to keep water needs to a minimum; our water is metered and it just seems crazy to put high quality drinking water on the garden. You wouldn't pour bottles of mineral water over the garden, so why use tap water, which is of similar quality? We collect rainwater, but there is a limit to how much you can save in water butts, so we don't want to create a big watering need as this can take some time with a watering can.

Our main strategy is to have perennial plants in the garden, these are well established and their roots tap into underground water supplies. Plants in our garden have to be fairly tough anyway as there are mature trees in our neighbour's garden on our north boundary and they take quite a bit of the water.

In addition, we have not only one rainbarrel on each downpipe, but two in series, and if there was room we would have more on each downpipe. During a rain shower lots of water comes off the roof and into the downpipe - what doesn't go into rainbarrels just goes straight into the sewer system. Therefore, if we collect as much as possible it can be used to water the garden and it doesn't contribute to the flood risk created by excessive run-off of rainwater. Thanks to my former colleague, Phil Wildbore, for this bit of inspiration.

We never water the lawn in summer when it's dry. OK a well-tended green lawn looks wonderful, but grass is adapted to dry climates and actually survives a drought much better than some other plants. It will always come back when the rain returns, so just look after it well in other ways and it will reward you.

We do have some hard surfaces around our garden. By far the largest part of these is covered with gravel, rather than tarmac or paving. This is also a good strategy because gravel soaks up rainwater, which is then available beneath the surface for the beds and lawn. Where there are impermeable surfaces the rainwater will run off, be lost to the garden and contribute to localised flooding problems.

It's been illegal for some time now to put down new impermeable areas in your garden. I've noticed the impact of this in our locality as people are opting to have gravel drives rather than paved drives. Our drive is looking worse for wear after several years and at some point we will have to consider one of the new permeable surfaces to replace the present tarmac.

I'll keep you posted!

Mechanical ventilation - to use in summer or not?

Mechanical ventilation with heat recovery is great for the cooler months, you get that fresh air feel without having to open windows and without losing all that heat you've built up with your central heating.

The question is though, should you leave it on during the summer or should you rely on opening windows? If you leave it on then it is using energy to ventilate your home, although with a summer bypass function there will be no heat recovery. The other advantages include not having insects coming in to bite at night or buzz around your food, and it reduces the disturbance from the inevitable increased noise in summer - planes flying, children playing, barbeques in the garden.

But it does use energy and you could just open the windows to create air movement and a cooling effect.

The first year we had our system we kept windows shut and the MVHR switched on - we knew the horrors of a fly infestation and didn't want a repeat! In a hot spell it was quite hot in the house, but then it would have been hot if we opened the windows; the MVHR certainly didn't act like an air conditioner.

This year we are using windows and blinds during day to keep sun out and allow fresh air in; we're putting up with daytime insects. Once there are lights on in the evening we close all the windows and use the MVHR to ventilate the house and that's successfully kept away the mosquito bites!

We try to keep our electricity bills down in other ways, i.e. nothing is left on standby, broadband is turned off when we're not using it, we use a laptop rather than a pc and this is put on standby if not in use for more than 10 minutes and turned off at other times when not being used.

So maybe the MVHR is our electricity indulgence, along with the fridge/freezer and phone. However, used intelligently we feel it contributes to good ventilation of our home without excessive energy use.

Has anyone else out there had experience of using these systems in their own home?

Clever use of blinds and curtains

Curtains and blinds can help improve the thermal performance of your house - more information. Since having ours installed we have learnt a lot about their effectiveness.

The first big shock was the effect of having our house decorated over the period early October up until Christmas last year. We had approached the decorator in May, but that was the best time we could get. Anyway we didn't have any curtains or blinds at our downstairs windows for that whole period; also doors were left open quite a lot during the day and on top of that we had snow from November. All of that led to a massive increase in our use of gas - it came as quite a surprise.

We have noticed some real benefits of our blinds since then. We have a Luxaflex Duette insulating blind on our patio doors. This stops quite a lot of the cold air coming through that large expanse of glass - and it does come through despite being double-glazed. If we raised the blind first thing in the morning we could feel that cold air trapped between the blind and the window and that was then coming into the room. So what we've been doing is waiting for the morning sun to warm up that layer of air, then we open the blind. We can then make the most of the solar gain from the sun coming in through the glass and warming the room.

During very cold weather we often left the blind closed all day as it gives the room a nice light feel even when closed and it's kept the room that bit warmer. At night we add thermally lined curtains to keep the house even more cosy.

Also when it is hot or too sunny we've used the blind to stop too much heat coming into the house. Glaring sun can be excluded by partially closing the blind; too much heat coming in can be prevented by closing the blind altogether to prevent that solar gain. The room is still nice and light but it is a cool oasis when it's been really hot outside. When it is cooler outside at night we've raised the blind to reduce temperatures indoors.

We have a north window that has a Luxaflex Architella blind, which must be about the most insulating blind on the market. We keep it firmly closed in the winter, which definitely reduces the icy draught coming down our stairs! In hot weather we can open it to help us lose some of the heat indoors.

We are seriously thinking about having these blinds in other parts of the house as we are so pleased with how they have worked. If we have another cold winter we hope to also notice the difference in our gas bills - it's clearly not enough just to have double-glazing.

Solar Panels working - it's great

Since we've had the sensor replaced our solar panels seem to be working better than before. As well as being replaced the sensor was also put in a slightly different position, so maybe that's why.

Between May 7 and September 24 2009 the panels were working for 246 hours total, about 1 hour 45 minutes each day on average. Between 18 May and today, 28 May 2010, they have operated for 56 hours, an average of about 5 hours 36 minutes a day. In addition, the water has been getting up to maximum temperature and has been working in clould as well as sunshine.

If it goes on like this then our gas bills will be even lower, which is great news.

We just need to make sure that squirrels/other wildlife don't take a fancy to the cable again!

The Mystery of the Solar Panel Sensor

I was saying 2 days ago that the sensor had broken on our solar hot water system. Well, the guys have now been out to fix it and the problem wasn't the sensor, it was our wildlife!

The cable had been chewed through and the sensor taken away. We don't know who the culprit was, but grey squirrel is at the top of the list of suspects. But magpies or jackdaws, with their liking for shiny objects, might be possibles, although it would be harder for them to break through the cable.

The squirrels have a track reocrd too! When the power to the garage was linked to the house by a cable along the top of the boundary fence they chewed through that wire and broke the connection. Every so often there would be a bright flash outside, like someone taking a flash photo, it took ages to work out what was going on. Presumably each flash was an electric shock for a squirrel, but it happened more than once so they weren't easily put off!

Let's hope that we don't have a repeat with the solar hot water sensor. This time black cable has been used instead of white and the sensor has been tucked away a bit more.

I'll keep you posted! I'd also be interested to know whether anyone has had the same problem - please let me know.
Carol Hawthorn