ASK THE EXPERTS
Whether you want to know how to solve water pressure dilemmas or choose the right heating for your self-build, our team of experts can help
This month our experts answer questions on plots, heating systems and new windows
Q We are currently searching for a plot to build a home on. Occasionally we come across plots with planning permission for three properties, for example. If we only want to build one home on the land what is the likelihood of getting planning permission for just one property?
ANON, VIA EMAIL
Getting new planning consent for just one home on such a site wouldn’t normally be a problem.this is because the main issue will have been the principle of residential development on that site, and this will have been established via the existing consent. However, you will need to carefully design the new building so it meets all the current and any emerging (draft) design guidelines, including national, local and neighbourhood housing design policies. These can be a minefield to work through, so it would be a good idea to get some professional advice before coming up with a design that can then be submitted for your new planning consent.
That said, if you want to build just one of three or so houses exactly as already consented, then there is nothing to stop you starting the full three house project and just indefinitely pausing after you’ve finished the first one. Or you could build all three straight away and, especially if they are connected, use Permitted Development rights to combine two or more into one larger home. Best to check the exact zoning on this first though, as PD rights don’t apply in various parts of the country.
SIMON RIX, PLANNING CONSULTANT AT PLANIX.UK
Q We’re planning to convert our loft to create a master
bedroom with en suite. We’re opting for a shower but have a gravity fed system with a tank in the loft. What are our options regarding getting good water pressure? I’ve read we can move the tank higher in the loft for example? Or is it easier to install a pump for the shower? OWEN AND SARAH, YORK
First, check your water pressure rates.you can buy a water pressure device but a quick DIY route to find out is to run a tap into a jug for six seconds then check how many litres are in the jug and times this by 10. This will give you the litres per minute range — anything under 10 litres per minute is considered a low flow rate. Your installer will need to check that any product being installed is fit for use against the given flow rate or make amendments to your system to provide the flow rate needed.
As you rightly say, you can, in most cases, lift your tank to provide better flow rate. But this is not a small task and, more often than not, can work out as an expensive way to increase pressure as you’ll need to alter and recommission pipes.
The most effective way to improve pressure is to add a pump to the water system.there are three main types of pump categorised as positive, negative and universal.
Positive head pumps are for systems that have good flow rate from the water tank — this is usually if the shower is sitting more than 600mm below the header tank as the gravity feed works to force the water to the shower.they are usually suitable for showers with less than 0.3bar requirement, in my experience.
If you have poor water pressure and the shower head is either level with or around 600mm above the cold water tank then you would install a negative head pump. If you require higher pressures over 0.3bar, then you’d choose a negative pump, too. They work on an air pressure switch which kick-starts the pump for a more efficient flow rate.
Universal pumps suit both positive and negative head set ups as they are automatic and don’t need a minimum gravity flow of water to work. Universal pumps act as a booster at 1.8 bar. Generally one side has an additional booster, which is fitted on the hot feed to improve the balance of pressure. However if the goods being installed require 0.5 bar or more I would generally suggest a negative head pump. LYDIA LUXFORD, CUSTOMER AND TECHNICAL SERVICES MANAGER AT EASY BATHROOMS
It is not clear what part of Scotland you are in or the size of the proposed home so I will tackle things generically. The question that you are facing is one that is being asked by many self-builders. You have said that you do not want to use gas but if it is available I would still include it in the mix of options to be considered because the gas grid is becoming greener and in future the grid will also have a higher content of hydrogen as well as synthesis gas that is derived from the gasification or anaerobic digestion of organic waste.
FIRST, A WORD ON THE ELECTRIC SUPPLY
How good is the electric supply to the property? If you only have a single phase electric supply then you need to work out the balance of use. We will soon have electric cars and you need to determine how many miles of charge you will need to put in the vehicle. If this is indeed a home designed for the future then you also need to make allowance for the next occupiers to have different lifestyle requirements. For example: you may be able to charge your electric vehicle (EV) at work so can design in an electric heating system as you will not need the supply to charge the EV at night. The next occupant may be someone who has a 100-mile commute each day and will therefore need to charge the vehicle. Lets put that into context.your EV will deliver around 2 miles per kilowatt hour (kwh). A single phase charger will charge at a maximum of 7.4kw per hour. Therefore you can charge up around 15 miles per hour and on average you can expect around 150 miles from an overnight charge. A two car family will have to share that. A 7.4kwh charger will also draw 32 Amps.this is important because you need to check how many Amps you have available to the property. A single phase electric supply may have 100 to 120 Amps but could also be as low as 60 Amps. If you then add an electric heating system to the mix you may not have enough even with management software.
Assuming your electric supply is up to the challenge I will come back to the questions.
1 THE ASHP OPTION
An air source heat pump is usually a better long-term investment than direct electric heating. The initial capital cost is higher for the heat pump but the running costs should be considerably lower. Add to that the potential benefit of the Renewable Heat Incentive or the proposed Clean Homes Grant and the heat pump can look even more favourable. That said it will depend on the heat load of the home. A property built to Passivhaus standards could use more energy for heating hot
“The best investment is in the fabric of the building. Optimise the insulation and the airtightness and then design the heating system to match the heat loads. As the heat load changes so does the solution”
water than for heating the home, at which point you need to make sure that the heating system is optimised for that particular heat load.
2 THE ELECTRIC COMBI BOILER OPTION
When considering an electric combi boiler you need to work out how many litres per minute you actually want to heat. A 12kw combi boiler will draw 52 Amps and only heat around 5 litres per minute by 35°C. When the incoming water is colder than 5°C you may want to slow the water down to increase the heat.that is not great if you like a powerful shower. If you drop the rating of the combi boiler to 8kwh then you will draw around 32 Amps but only deliver less than 4 litres per minute.this is the advantage of fossil fuels in that they can deliver up to 40kwh (albeit on a small property you may only actually want to install a 24kwh boiler) but it is at least twice the flow rate of the biggest electric boiler. By using a hot water cylinder you can at least use a lower capacity heater
3 THE SOLAR PV OPTION
and get a better flow rate in the shower. You may also consider a micro heat pump which is integrated into the hot water cylinder. If you are going to be living permanently in the property then solar photovoltaic (PV) panels could be a sound investment. Check online (PVGIS) for the solar resource in your area and look at your annual electricity use and see how much of the generation you can in fact use. This will then give you a good indication of the potential return on investment.the PV panels will also provide a lot of the energy required to heat a hot water cylinder, especially if it is a micro heat pump as they only draw around 650 Watts.
The best investment is in the fabric of the building. Optimise the insulation and the airtightness and then design the heating system to match the heat loads. As the heat load changes so does the solution.