How to turn a lovley old house with solid walls into a warm efficient home

AIR SOURCE HEAT PUMP - MECHANICAL VENTILATION & HEAT RECOVERY

SPACETHERM INTERNAL WALL INSULATION - UNDERFLOOR HEATING

NEW HEATING SYSTEM 

Prior to be beginning this project my home was heated by an oil-fired Rayburn. It looked lovely, and was wonderful for sticking your cold butt against when you came in from an invigorating winter walk. On the downside, it burnt oil at a similar rate to a Formula 1 car burns... Formula 1 car fuel. I was determined that it had no place in the 'new' house. With my improved insulation levels I made the decision to purchase and install a heating system based on an Air Source Heat Pump. My earlier article details my lengthy reserach on the subject.

However, I learned that simply installing a heat pump instead of a conventional boiler is only half the task. For a heat pump to work efficiently then heating distribution system has to be suitable. Not addressing this issue is, I believe, why there are those out there with poorly performing heat pumps. The key is to not guess but do the necessary calculations to ensure you can deliver sufficient heat to your rooms with a CH water temperature significantly lower than a traditional system. I would suggest a design water temp definitely not exceeding 45 degrees, but lower still if you can.

[col class="span8"]There is much talk aboiut whether radiators can be used effectively with a heat pump or whether it has to be UFH. I beleive that either can work. With either system you can get the figures and do the calcs to ensure sufficient heat is being delivered at the appropriate temperatures. Obvioulsy, a good heat pump installer will look at this for you and advise you rather than simply 'plug' a heat pump into any existing heating system (unfortunately, not all installers are good). Generally it is no bad thing to either examine in detail any calculations offered by a company or do your own.

If you choose to use radiators it will undoubtedlly be necessary to have much larger ones than with a traditional boiler. Depending on the nature and layout of your home this might be easily accommodated or a real pain. Underfloor heating is a natural way to go, but of course this is very disruptive so it will depend what level of home improvements you are undertaking as to whether this is an acceptable route.

installed UFH throughout the ground floor, both in the new extension and retrofitted to the old house. Details of the former are on my sister site DIY HOME EXTENSION and details of the latter are on this site under the FLOORS menu. I laid UFH in the new bathroom and en-suite upstairs but added larger radiators to the bedrooms as I did not want to mess with the old elm floors.

The purpose of this article is to discuss my running and tweaking of the system and how effective it is.

It is important, even at the design stage, to consider how you will use your heating system. I have met many users of UFH that claim it is rubbish. However, this is because they try to use it like a conventional heating system, turning it on and off a lot for the mornings and evenings. Certainly a UFH with large thermal mass - ie. UFH in screed or concrete can not react quickly, so a lot of on/off is not appropriate. Unfortunately, many people do not like the idea of leaving the heating on for long periods, fearing it will cost the earth. There are now many new systems for laying UFH available, however, and not all involve a large thermal mass. Systems using cement board or similar are intended to work more like a conventional heating system and because there is less mass they react more quickly. They may also be less disruptive to install, especially if you have good head room and can lay over existing floors. Radiators will also offer a quicker response than traditional, large mass UFH.

All that said, there is nothing wrong with large mass UFH provided you use it apporpriately. Indeed, I chose to go this route and have very large mass throughout my ground floor. My design plan was that most of my heat would be generated from my downstairs UFH and percolate through the house. On the first floor I would have the lower mass UFH for the bathroom and en-suite, but the bedrooms, which we do not like very warm anyway, would have minimal direct heat applied, though they all did have large radiators fitted.

I began using my heating system running a water temperature of 40 degrees and appropriate roomstats to switch on and off at 20 degrees for the main downstairs rooms. I also set the timer to allow a drop of a couple of degrees overnight, thinking a couple of degrees drop would not be too much to regain in the morning. This worked ok and monitoring my heat pump usage was proving cost effective. However, as I work from home a good deal anyway, and I was curious how low I might take the water temperature I had a fiddle, lowering the water temp bit by bit. Last winter 2014/15, which I think was fairly typical of an English winter, I decided to keep reducing the water temp to a level where it could not quite get warm enough to meet the roomstat temp of 20 degrees on a cold day but just did on an average day for some of the loops, but kept it running 24/7. Basically, the water temp was dictating rather than roomstats. In the end I reduced the water temp as low as 28 degrees. This kept the rooms at an acceptable level and I would spark up the woodburner for the evenings when my wife got home. This very quickly raised the main lounge from acceptable to nice and toasty. For me, this system worked well and was slightly more cost effective.

I think that because I have the heat recovery system it helps distribute the heat throughout the house. Before I undertook my home improvement it was a typical old house with hot rooms and cold rooms, now it is all very comfortable with no drastic temp changes, though we do like to keep the bedrooms on the cooler side.

© Christopher Thompson