Wednesday, 16 July 2014

Air con at home?

I am getting quotes. I have decided my new "den" (AKA ex.garage) will have proper air-con. Not sure yet if ceiling mount like the office, or wall mount.

But what of the rest of the house?

Basically, during the winter, a heat pump is pretty efficient as a way of heating even compared to gas - right?

During the summer I am fed up with it being too damn hot. Yes, even in the UK.

Now, I have problems...

I can easily do a couple of the bedrooms, but need to find some really quiet internal units for that. Hopefully such things exist.

Getting the living room done will be harder. I could take the view of "sod that, I have my new 'Den' and don't care" but maybe I should try. I probably need to find a way not to have a visible internal unit. Ideally it needs to be something mostly external that appears as some innocuous "vents" on the wall high up internally, else it will not get approval. Basically Sandra puts "how it looks" way above "how comfortable it is" which is a challenge for some rooms.

It won't be cheap, I am sure, but I would assume this has to add value to the house. Overall I am not against spending some of my hard earned money on creating an asset. That said, there is a lot to be said for being "comfortable" regardless.

Getting some people in to quote real soon now.

Any constructive comments welcome.

10 comments:

  1. A ducted unit might be better for some of those rooms - the room itself just gets some vents, with a short duct running into a unit up above in the attic or whatever, which sounds like exactly what you have in mind. (Plus a single unit could deliver cold air to multiple rooms at once, unlike in-room units.)

    I'd love such a setup myself, if only funds permitted! What I might do in this case is just cool the bedrooms and staircase/hallway from the attic: it wouldn't be perfect, but since heat rises and cold air sinks, with the house being quite well insulated I suspect it would make a welcome difference downstairs as well.

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  2. I would be surprised if it did add any value to the house.

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  3. Heat pump units are supposed to have an efficiency of 300-400% however you can't do away with the gas central heating as they can have issues in cases like when there is freezing fog outside. The outside units will freeze over very quickly and frequently have to switch into defrost mode so you will only get short periods of heating.
    Personally I just have one in my bedroom and I find if I switch it on and leave the bedroom door open the cool air does tend to roll down the stairs and keep the living room cooler as well. So depending on the layout of your hose a ceiling unit mounted into the loft situated above the stairs may let the air drop down and cool the living room.
    I would highly recommend the Daikin models as they have units specifically for the bedroom which have an ultra quiet fan mode. Mine is by far quieter than any regular desk fan that I have come across. I live in Warfield so you are welcome to come over and see for yourself how quiet they are.

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  4. http://www.daikin.co.uk/minisite/daikin-emura-ii/index.jsp
    Take a look at the brochure. 19dB(A) in quiet mode and it might be stylish enough for you to get approval for the lounge. Plus it has wireless control so that will give you something to have a play with :)

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  5. I had air con installed a few months ago. Summers were hell because I just couldn't sleep with the heat, and if I came home after an evening out it took hours with the windows open to cool the house. It's a small 3 bedroom house with stairs that rise out of the lounge, I live on my own and don't need anything larger. I went for a standard mini split system (but quite a large capacity one). The internal unit is mounted on the landing wall high up near the ceiling, and directly above the stairs. This allows me to direct air across the landing into the main two bedrooms (mine and my parents when they come to stay) and also cold air drops down the stairs and cools the lounge quite well. What this doesn't cover so well is the dining room and kitchen which are through an open door off the lounge, it's often 22 degrees in the lounge and 23 or 24 in the dining room and kitchen but they are on a west facing wall and get a lot of sun in the afternoon.

    The pipes for my air con go up into the ceiling, across the loft and down the wall outside the house to the external unit under the dining room window. I had the pipes put inside a new rainwater downpipe, this makes the installation less obtrusive and matches the existing rainwater downpipe. It also means UV can't attack the foam insulation, we have some at work that is falling off after 5 years of UV degradation.

    I need a condensate pump because being a middle of row house there is no external wall for a direct drain out of the back. Make sure the outlet of the condensate pipe is in free air, mine wasn't and this caused the pump to back up and drip inside the house.

    My biggest problem was actually installing a new mains feed heavy enough to run the air con. The power goes to the external unit usually, and my consumer unit is at the front of the house. I did this part myself, I ran a new feed from the consumer unit all the way up into the loft and then across and back down to the outside. The air con company didn't seem to know much about the mains, which is why I did that part myself. So make sure you consider the mains feed, I recommend a dedicated MCB in the consumer unit for it.

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  6. On the subject of heating, mine can heat but that isn't why I bought it. It does mean I have some backup heat if the central heating fails for some reason.

    My understanding is that a heat pump is about twice as efficient at heating as generating the heat directly in say an electric fire. Given that electricity is about 7 times the price per kwh as gas, this means air con heating is about 3.5 times more expensive than gas (assuming 100% efficiency for gas, and many condensing boilers are over 90% efficient these days). My numbers are a few years old, efficiency of air con may have improved and relative prices per kwh may be different. Do the numbers and see what it says.

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    1. A bit of Googling earlier showed me gas+electricity prices here with a ratio of about 1:3, and heat pump efficiency of 3:1 for pure heating mode (better when it takes waste heat from somewhere else), which would make it roughly equal to 100% efficient gas heating. As I recall (having bought one!) those 90% claims for condensing boilers are rather "optimistic", which would give the heat pump a 10+% edge. (Not to mention the snag when you discover, at 10pm in a -20C winter, that a certain large gas company didn't bother insulating the long run of condensate pipe, which then froze up...)

      A dedicated mains circuit might be overkill for anything other than the biggest a/c unit: because of that 3:1 ratio, a "9kW" unit is only taking 3kW of power - i.e. a regular 13A socket would do.

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    2. I use mine in heating mode if I am away at the weekend. I just turn on the aircon in the bedroom when I get home set to about 16C and it stops the bedroom from becoming too cold overnight. Then the following day the central heating is on as normal so its a reasonable temperature when I get home from work.
      That way I am only heating the one room that I need which makes it far more efficient.

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  7. Yesterday I was fitting a new lock onto a south facing door on the back of a shop. Full sun and hot enough. However, even worse, the vent fan from the a/c was blowing 45 degree air across the way as well.

    So if you position your external heat exchanger on the patio it will be great for those long evenings when it gets a bit chilly - turn on the a/c inside and take the chill off without lighting a fire or anything. A handy added benefit of planned in advance.

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  8. have you looked into Heat Recovery systems? Every room has an air duct, in the living rooms it feeds air in, and in the kitchen and bathrooms/loos it takes it out. In the loft there's a Heat Exchanger that takes the outgoing warm air and uses it to pre-warm the incoming air. You can add a reversible heat-pump to go beyond just the conducted-heat exchange, and also to use it for cooling. Installing it will be disruptive, but so will installing any sort of "central air" as they call it in the 'States. The only possible issue I can see is controlling individual rooms - not sure if they provide for that.
    I think the Self-Build place in Swindon (I forget what it's called) has examples you can look at.

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