MrM

Given the cost of the wall inverter units are about £300, I might as well not bother servicing them and if they last me 4 years I will be quids in.

This company claimed if we installed Daikin wall units as part of a multi line air to air setup, that each one would require an annual service. What would be involved, I dont know at this time. Ive had 2 independent quotes back at about the same price, so unless I do it myself, this will rule them out on economy.

And in the quickest 180 ever, Ive just learned that servicing air con units would be £85/year x 3 plus vat. So £300 a year! Im expecting that to be multiples on what I spend on electricity to service this building each year, which all of a sudden makes it look quite uneconomical!

After much more deliberation I feel Im settled on air to air via multi split line. If it were our main house, UFH would be an obvious choice. Due to the adhoc nature of how we will use it, air to air seems to offer a bit more flexibility and responsiveness and the benefit of cooling in the summer would be a bonus. The main penalty is losing the DHW heating. A Daikin system has been recommend and will look to pursue that line, 8.5kW heat pump with either Emura or Stylish wall units. To anyone who has fitted a multi line system, is there anything specific I should bear in mind when thinking about design and placement? I have been recommended to put the units themselves above doors, since that area is somewhat dead space and will not be blowing air directly onto anyone. With regards to piping, anything specific to consider there? Many thanks

Thanks for the explanation ProDave. I think Im sold on the ASHP. I now need to decide on air to air, or air to water. Given how I plan to use the rooms, I'm inclined to think air to air would be more suitable to our needs; more responsive if needed at short notice, only on shortly before or when we need it and not all the time like UFH. Would anyone argue otherwise? Only downside I can see is the bulk of the unit on the wall, and the fact I would need a separate hot water solution?

Thanks for your comments, all very helpful. In warm weather I guess the pump wouldnt be on to heat the UFH, but might be on at some time if we were to heat hot water using it. I'd like to learn more about the hot water side of things, please forgive me if these are basic questions. What size heat pump am I likely to need to cater for UFH and to heat hot water in a cylinder? What kind of temp should I look to heat hot water to in a cylinder (excluding any one off immersion boost to kill off legionella) and thus what size cylinder to cater for a shower for 2 people? Any idea how long I should expect for the cylinder to heat to the recommended temp? Thanks again

Thanks ProDave. Being a new build I would be disappointed if insulation and air tightness weren't top notch. The condenser would be in the corner of a garden which we will sue for leisure, the area is approx 20m x 20m. If we were sat in the middle, would the noise be an annoyance do you think?

So after further meetings with our builder and architect we have decided to drop the wet CH idea. Choice is now electric radiators in each room, or underfloor heating with an ASHP, and aiming to have that heat water in a cylinder too. My concern is whether UFH is best for our needs. As above, the office and bathroom will be used often, gym and bedroom less so. I dont want to heat the floor unnecessarily, but also dont want it to be cold when we do want to use those rooms, especially the bedroom. Any idea what running costs would be like to keep the building at 16c? Another concern is noise from the condenser, is this particularly bothersome? Thanks again

Ive attached a floorplan. Ignore any comments re finish and materials as this can change. Original plan was to split the feed from our U6 gas main. Our meter is approx 12m from the road. This outbuidling is approx 35m from the meter. It was deemed by our engineer that if we tee'd off of the existing connection that we would have insufficient pressure and potentially flow for a boiler in the main house (~30kW) and a small combi in the outbuilding. A preliminary estimate to upgrade to a U16 meter was approx £4k and would mean digging up a mature garden to do so. Likewise a trench from the meter to the outbuilding would be very disruptive. It seems fewer engineers can service U16 meters, so all things considered, for the amount we will heat the outbuilding, we are looking at electric. Given the original plan was wet CH heating via gas, the obvious step was the same via electric. I spoke to a few local engineers who install ASHP's and received mixed advice, with some saying for the usage, stick to an electric boiler solution. My plan was to install a separate E7 circuit, heat rooms if required before 7am, and same for a short boost of hot water. Then top up either if needed later in the day. I do have concerns an electric shower wont prove robust and powerful enough for our desire. I also have some issues with how they look and wont fit with our bathroom design particularly well. We live in a conservation area, so I cant place numerous condensers outside of the building. I would need to make do with one condenser at the rear for any AHSP solution we were to put in place. The air to air solution is interesting, especially to provide cooling in summer, but when I looked at cost it wasnt cheap (Daikin multi split solution with 5 units was approx £4.5k and plenty of reviewers seemed to run into problems). Above all else I would like a hassle free solution that works with minimal maintenance and I am willing to pay a small premium for this.

Thanks ProDave, if you dont mind I have a few questions. Would you be able to elaborate on the heat pump side of things? I presume you mean scrapping radiators altogether in favour of a wet underfloor heating system that would always be on? How would this cope in a cold Winter? Do you have an example of a heat pump I can look into? We are planning on installing vinyl laminate (Amtico/Karndean) in much of the build, with some kind of shock impact rubber flooring in the gym. Would this impact the underfloor heating aspect in your opinion?

First post from me, I am hoping for a little bit of advice from anyone who has had experience of using electricity for their heating needs. In brief, we are currently building an outbuilding close to our main house which will require heating (total of 5-6 radiators, no more than 20,000 BTU total and unlikely to all be needed at once) and a bathroom (shower only). This outbuilding will house a guest bedroom, a small gym/exercise space and a home office. Our main house has a standard U6 gas meter. The run from the meter to where we would look to site a boiler is about 35m and we have been told we would need to upgrade our meter which we have ruled out on cost. We cannot easily store LPG. As a wildcard I looked into air to air heat pumps, which look interesting, but very expensive to install and would not solve our hot water situation. We live in a conservation area so installing solar panels on the roof is a no go. It looks like electricity is really our only viable option and I plan to install a wet CH system and I am looking to use a Honeywell Evohome thermostat solution and so only heat individual rooms as needed to run as efficiently as possible. Whilst I am not too concerned about running costs, due to level of insulation and the relative infrequent use of the building we need to be as economical as possible. I would anticipate we will use the office space 4 days a week, the gym space three times a week and the guest bedroom on an adhoc basis. My main concern is the heating of hot water for the bathroom as this will only be needed on demand. As I see it we have 2 options, a heat only boiler twinned with an unvented cylinder, or an electric combi. I am concerned that we will incur costs heating and storing water and not needing it if we install an unvented cylinder, but this would give us reasonable pressure in a shower. I realise the ecombi is relatively new technology and the advice I have been given is to stick with the more tried and tested solution. As such I am keen to hear about peoples real life experiences with ecombis. I have been looking into products from EHC and Elnur, which both appear to have some internal hot water storage (for instant demand) which is fine, but what then happens should this store run out? I am hoping to avoid guests having a cold and weak shower if they come to stay with us. Thanks for taking the time to read