RefurbN16

Tag: Boilers

  • Sustainable Refurbishment – Towards an 80% Reduction in CO2 Emissions

    The UK’s building regulations didn’t start to consider energy consumption until the 1960s, when very basic requirements to conserve energy were placed on house builders. These requirements have slowly been tightened over the decades and the introduction of the Code for Sustainable Homes has accelerated this in recent years.

    The intention is that new build homes built from 2016 will be zero carbon (although the exact definition of ‘zero carbon’ in this case is still up for grabs). The problem is that the UK’s housing stock is the oldest in the developed world, with 8.5 million properties over 60 years old and an estimated 24 million homes built up to 2016 expected to still exist in 2050.

    Zero carbon new build homes are definitely needed so that new homes don’t add to emissions, but all of the carbon reductions will have to happen in homes that have already been built.

    In the previous post we looked generally at a whole house approach to sustainable refurbishment. The Energy Saving Trust has recently published an interesting new publication which looks at this in more detail and points the way towards an 80% reduction in CO2 emissions in existing homes. This guide is aimed at homeowners as well as housing developers and builders and is clearly written and nicely presented.

    It gives an excellent overview of the energy efficiency measures that can be implemented in the UK’s homes including the different types of wall, roof and floor insulation, improving windows and doors, increasing air tightness as well as efficient heating and hot water systems and lighting and appliances. Also covered are microgeneration, water efficiency, waste and recycling and even climate change adaptation.

    If you want to get a good picture of what needs to be done to our homes, then this is a good starting point. Hopefully it will stimulate you to consider which of these measures can be applied in your home.

    The Energy Saving Trust has lots of interesting technical guidance. More information can be found here.

  • Boilers Pt 3 – Boiler Brands

    Replacing your boiler is an expensive undertaking and it’s not hard to find stories of boilers dying in fairly short order.

    Like most things in life, you get what you paid for and boilers are no exception. Cheaper brands are likely to use cheaper components that are more prone to malfunctioning and can easily cost you more in the long run.

    But if you buy a good quality condensing boiler and it’s installed and maintained well, there’s no fundamental reason why it shouldn’t have a long life of delivering substantial energy savings. But which boiler brand is best?

    There aren’t any scientific comparisons, but the excellent consumer magazine Which? ran a survey (sub required but you can get a one month trial for £1) amongst 3,000 of their members who had purchased condensing boilers since 2005, rating customer satisfaction.

    The survey found the highest customer satisfaction came from Vaillant and Worcester Bosch customers. Runners up were Vokera, Potterton, Glow-worm and Baxi.

    The boiler scrappage scheme is currently underway, offering £400 for the replacement of a G-rated boiler with a new A-rated condensing boiler. You can find out if your boiler qualifies by checking here.

  • Boilers Pt 2 – Condensing Boilers

    In Boilers Pt 1 – Regular Vs Combi, we looked at the two main types of boiler which you find in the home. This post takes a look at replacement boilers, in particular condensing boilers.

    Since 2005, the Building Regulations have required that if you replace your boiler, you have to replace it with a condensing boiler. There are a few exceptions to this (see Appendix A here), but essentially all new boilers condense. But what does this mean?

    A condensing boiler is not all that different to your old boiler, but it is more efficient. To achieve this, condensing boilers are fitted with an extra heat exchanger. The heat exchanger transfers heat from the burning gas in your boiler to the water in your heating or hot water system.

    A heat exchanger is a very simple metal component through which water is passed. It has a large surface area which makes it easier for the heat to pass from the hot burning gases to the cooler water in the heating or hot water system. A radiator is an example of a heat exchanger, passing heat from the hot water to the air in your home.

    By adding an extra heat exchanger to the boiler, more heat can be extracted from the hot gases that would otherwise escape up the flue and into the atmosphere. This energy goes into preheating the water returning from the heating or hot water system, before it passes to the main heat exchanger to be heated up the rest of the way.

    The “condensing” part refers to the moisture (or “condensate”) which condenses out of the gases and is flushed down the drain. The action of condensation transfers additional heat to the heat exchanger (see here for the Wikipedia explanation).

    Condensing boilers reduce the temperature of the flue gases from about 150°C to about 55°C so there is a substantial amount of heat there to be recovered but they won’t always be in condensing mode. In order for this to happen, the temperature of the return pipework (which carries the water back to the boiler after passing through the radiators) has to be below 55 degrees.

    For this reason you need to make sure that a regular boiler is correctly sized for your home. This is one of the reasons why you should reduce the heat demand of your home as much as possible through insulation and draught proofing before replacing your boiler. If you do it the other way round, your boiler is likely to be too big and it won’t work as efficiently.

    Your boiler thermostat also needs to be adjusted so that the flow temperature (the temperature of the water leaving the boiler) isn’t so high that the return temperature is too high for the boiler to enter condensing mode. I’ll cover this in more detail soon.

  • Boilers Pt 1 – Regular Vs Combi

    Existing boilers in UK homes fall into two main types – regular boilers (which might also be called “heat only” or in some cases “system” boilers) and combination or “combi” boilers.

    A regular boiler delivers heat to both the heating system (usually radiators) and a separate hot water system which takes heat to the hot water cylinder. A hot water cylinder consists of a metal tank, hopefully well insulated, inside of which is a coil of tubing. The boiler passes hot water through this tube and this indirectly heats the water in the cylinder.

    So instead of taking the water to the boiler you take the heat to the cylinder. When you turn on the hot tap, hot water is taken from the top of the tank and replaced with cold water at the bottom.

    A combi boiler on the other hand, supplies heat directly to both the radiators and to the cold mains water so it directly heats the water itself and delivers it on demand to the hot taps. Combi boilers store no water and so they avoid the problem of sometimes heating up water that  just sits there cooling down (known as standing losses).

    Now you may be thinking “why bother with a regular boiler and hot water cylinder if you can avoid those losses?”, but there’s a catch with combis: they heat water less efficiently than regular boilers. So there’s a trade off between the benefit from avoiding standing losses and the penalty from reduced hot water efficiency.

    The upshot of all this is that a combi is most suitable for smaller homes with a low hot water demand while a regular boiler is most suitable for a home with high hot water demand. Combis are also more suitable in smaller homes because they don’t need the space for a cylinder.

    In my flat I unfortunately have a cylinder which means that I don’t use anywhere near the full amount of hot water. But it is very well insulated with factory fitted foam which means that I just have it come on once before I get up and there’ll still be hot, well warm, water when I get back in the evening.

    There is a trend at the moment towards the inappropriate replacement of regular boilers with combis but it should be resisted. If anything, removing the cylinder makes it that little bit harder and more expensive to install a solar hot water system, which needs as much storage capacity as possible, so if you’re considering going down this route you should try and keep hold of your cylinder.

    Next up we’ll cover high efficiency condensing boilers. If you want to read in more detail about gas heating systems then your best bet is to check out the Energy Saving Trust publication Domestic heating by gas: boiler systems (CE30)

  • Boiler Scrappage Scheme Launched Today

    The other big news today was the launch of the boiler scrappage scheme by the Department for Energy and Climate Change (DECC). The full details of the scheme can be found here, but here is the 30 second version…

    The scheme is offering 125,000 homes a £400 voucher on a first come, first served basis if they scrap their G rated boiler and replace it with an A rated condensing boiler. Condensing boilers are more efficient than conventional boilers because they extract additional heat out of the exhaust flue that would otherwise escape into the air.  They shouldn’t be confused with combination (combi) boilers which are boilers which don’t have a hot water tank, heating the water directly instead.

    The building regulations require (with a few exceptions) at least a B rated boiler to be fitted so this is pushing the bar a little higher, which is a good thing.

    The way it works is that once you’ve identified your G rated boiler and have received a quote that you’re happy with, you contact the Energy Saving Trust. From January 18th, cashback vouchers will be sent out and you should receive the voucher about 10 days after application. You then have 12 weeks to have the boiler installed and the voucher signed off by the plumber.

    A word of caution… You might well be quoted wildly different figures, some of them way too high (naming no names of course), so make sure you get a good selection of quotes. If you can find a good local plumber recommended by word of mouth, that might be the best way. Just be aware! There’s also a wide range of boilers. Some are cheap but poorly constructed and with expensive parts.

    You can find out if your boiler is G rated here. If you’re having difficulty, post a comment and I’ll see if I can find it (it’s not always completely obvious).

    Now while this is a good offer (it’s equivalent to a discount of about 15% to 25%), it’s really best to consider reducing your energy demand before you replace your heating system. This will mean that the boiler can be correctly sized to the heat demand of the home. Having said that, this is a one-off offer and is highly unlikely to be repeated.