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108 posts

Master Geek
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Topic # 150536 25-Jul-2014 20:30
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Hi there

We have a very small property in Wellington which our asthmatic daughter, her partner and our wee baby grandson rent from us.  It's tiny at 60m2 all up with an open plan lounge and kitchen, with the bathroom and both bedrooms off the lounge.  It is the end unit of a set of concrete block units, and has ceiling insulation.

They currently have a wall mounted heat pump which we have been told at 3.2kw is far too small to heat the home.  

We really need to put a ventilation system in to help with condensation and our daughter's asthma and the fact that there is a baby in the house who has been very congested over winter.  We've read a lot of forums on here regarding various ventilation systems and it seems we'd need to get something a little more expensive than the basic HRV type, so we can have a proper heat recovery unit. 
*  (The forum posters here sure are right re HRV, they tried to tell us their system could on a good day increase the home temperature by up to 5 degrees! )

So we're looking for some advice as to how we should go about this.  We don't want to spend heaps of $ on a system that we won't be able to recover on selling it when the 'kids' move on in a few years.

Can someone please advise on the following:

* Would a heat transfer unit help by moving heat from the closed off lounge/kitchen to the bedrooms, even though the heat pump is too small for the whole house?  Perhaps a heat recovery/exchanger unit within a ventilation system help with this?

* Would anyone know if it might be worthwhile (economically) to move the small heat pump to the baby's room then put a (new) larger system in the main area?

* Has anyone heard of opportunities to purchase ex-showroom models of heat pumps at a good price?

*  Are there any systems which will both heat the house and ventilate (albeit at different times of the day)?  I understand some of the wall units do this but of course they don't offer the heat exchange properties.

We've done a lot of research and it's all rather confusing as to what would be our best options, so would really appreciate advice.

Many thanks   :-)









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13977 posts

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  Reply # 1095865 25-Jul-2014 20:34
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I have some thoughts. I'll reply tomorrow properly, bit busy tonight.




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Master Geek
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  Reply # 1095879 25-Jul-2014 20:55
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Great, thanks Timmmay.  Look forward to your suggestions   :-)



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Master Geek
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  Reply # 1095915 25-Jul-2014 23:31
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Hi again

Further to my post, I believe we now have an answer to the heat pump being too small.  An oil heater can be used in the baby's room before/during his daytime naps and night bedtime - it should only cost about 45 cents per 2 hours to run so that is manageable.  The oil heater could then (once baby is well asleep and cosy under his blankets) be transferred to parents' bedroom.

So that probably solves at least the issue of the heat pump being too small - unless anyone has better ideas or other suggestions?

Thanks again in advance ...

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  Reply # 1095960 26-Jul-2014 05:05
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Only insulation has a positive economic benefit in most circumstances. But there are subsidies that are available for tenants and landlords so you should look at that option on EnergyWise.

You won't recover the cost of any insulation or system if you are selling in a few years. But if you can get a subsidy then the it becomes more attractive. Without a subsidy, your options cost thousands so you would lose most of that when you sell. That applies to heat pump, ventilation, heat transfer, or heat recovery/exchange (which is not what HRV provide). Having said that the costs of ill health can be much higher than that. So what is it worth to have your child and grandchildren healthy?

If you were to spend $3,000 on a system then that is $1,000 a year or about $3 a day. That will buy about 12 kWh of electricity on an average day. Assuming it's not needed in summer then you can have up to 20kWh during winter which could be used to heat the house better. That should be more than enough on top of what they're already using.

You don't mention how the flat is ventilated at present. It is one of the keys to removing condensation which is difficult to get rid of on uninsulated concrete walls. Any moisture also makes it harder to heat the room because it can absorb a lot of heat. I imagine that the flat is not ventilated enough at present. So do the usual things to keep moisture out: don't air clothes inside, try to open windows during the day, have an exhaust fan in the bathroom, keep the bathroom door closed to keep damp out of the living area, etc.

The current heat pump sounds like it might be too small to have been properly sized for the living area. They perform more efficiently if they're not running at full power. So it is probably worthwhile to open the doors to the bedrooms and run the heat pump during the day to get better efficiency and raise the background temperature. Then use electric heaters to boost the temperature at night.

Anyway, 3.2 kW is not enough to be transferring heat to the other rooms.  You need a substantial temperature differential to make a difference and that is usually provided by a wood burners and the like - they can commonly produce more than 10 kW.

If you put a heater in the babies bedroom then you should leave it there to keep the room warm enough all night.

There's more I could say but you should check out old threads on these topics.

[Edited to fix link]



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  Reply # 1095963 26-Jul-2014 07:18
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if the bedrooms are off the lounge why not just open the doors and leave the heap pump running?

3.2km isnt too small to heat a house of that layout you can do it, its just inefficient in doing so, and a heat transfer kit isnt going to change that. we have a 5kw unit that heats our house and our bedrooms are at the other end from the heat pump, we just leave the hall door open and shut all bar the rooms we want to warm up. it doesnt make it the same temp as the lounge but it does make it warmer than with out. but then we are not trying to heat the bedrooms just the living areas.

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  Reply # 1095992 26-Jul-2014 10:30
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I would suggest a heat recovery ventilation system, I've posted links to good ones on other threads, Cleanaire is one good brand that's reasonable value, and Drivaire have a good system but I don't think it's heat recovery.  The ventilation system will distribute the warm air around the house. Make sure you find a system that turns down at night, even though it recovers heat you still want to minimise noise and air movement at night. The people who sell these things want to change all the air in your house like three times an hour or more, which to me sounds excessive. This will reduce condensation, but if you want to eliminate it get some retrofit double glazing, the kind that they put a thick plastic sheet beside the existing glass, much much cheaper than replacing the window and almost as effective. It changed our house from having windows so wet we'd saturate a towel per window every morning in winter to just a light mist. Our little old DVS, not a heat recovery unit, runs during the day to push the damp air out, I don't like it running at night because of the sound of the old unit. 

Upgrade the heat pump to a larger model and sell the old one. I wouldn't suggest a heat pump in a bedroom as it's loud and moves air around, many would find it makes sleep more difficult.

Of course insulation is crucial. If it's old you may want to put another layer on top of what's there. 




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  Reply # 1096000 26-Jul-2014 11:06
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If humidity is the concern, then run a dehumidifier. They are cheap to buy, not expensive to run (unless you get the fancy desicant ones that can dehumidify a cold house) and produce usable heat, just not a lot of it.




Richard rich.ms

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  Reply # 1096038 26-Jul-2014 11:31
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If you have bare block concrete blocks consider lining them. You do it by fixing battens to the concrete blocks, and then gibbing to them. You can put polystyrene in the cavity which is surprisingly good and make it feel much much warmer. You may need a membrane barrier on the concrete if it gets moisture coming through. This has the added benefit if redecorating and making the flat more attractive and easier to sell.

I would start with that, a dehumidifier and electric heaters in the bedrooms. The paybacks for more heat pumps don't stack if you are looking to sell in the medium term.

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  Reply # 1096040 26-Jul-2014 11:37
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How often does the heatpump in the lounge run?  Do you run it overnight?  With a layout like you describe I don't think a heat transfer would be any real benefit, you may as well just leave the doors to the lounge ajar.

We have an oil column heater in our 1yo daughters room that we're using over winter.  Its thermostat controlled and from the energy graph appears to be on (drawing 1kw) for approx 10mins then off for 10mins.  So say 12 hours per night @ 50% usage @ $0.23 per kw/h and it roughly costs $1.50 per night.  When the wife gets up to feed overnight her room is always toasty.

The only system I know of with heatpump and ventilation in one system is the integra, but thats mega $$$ and way overkill for your sized unit.  http://smartvent.co.nz/integra/

We have an heat recovery ventilation system (SmartVent), but our primary heat source in the lounge is a woodburner.  A standard ventilation system will only bring cool roof space/outside air into the house, so if you went with this option you probably want to turn it off overnight (which unfortunately is when most condensation is created).




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  Reply # 1096060 26-Jul-2014 11:57
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richms: If humidity is the concern, then run a dehumidifier. They are cheap to buy, not expensive to run (unless you get the fancy desicant ones that can dehumidify a cold house) and produce usable heat, just not a lot of it.


They can use a bit of power, can be quite noisy, and it seems more like fixing the symptoms than fixing the problem. I guess fixing the problem would be removing the things making the moisture, ie people, so that's not very practical.




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  Reply # 1096073 26-Jul-2014 12:18
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I don't consider $1.20 a day or so to be expensive to run. Once the place is dried out they back off considerably with their usage. Yeah the cheap ones can be noisy but so are fan heaters and people tolerate those fine.

No point spending 1000's on a ventilation system which will have higher running costs or even more on a heat recovery ventilation on a place that is a rental.




Richard rich.ms



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Master Geek
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  Reply # 1096097 26-Jul-2014 13:09
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Thanks everyone for your comments.

Thanks Hammerer for the heads up regarding subsidies - I've emailed them on the off-chance they might help with a bigger heat pump or ventilation system.  The property has ceiling insulation and the concrete blocks are lined, so that's positive  :-)   Currently the flat is ventilated only by opening some windows during the day.  They don't open the windows at night as it's too cold.

Jase, if they run the heat pump with all adjoining doors open it seems to take forever to heat up since the heat pump is too small.

Timmmay, based on some of your earlier posts we've asked Cleanaire for a quote.  They do seem to have a very good system.  Retrofit double-glazing is also an option but there wouldn't be much room away from the original window to create space between.

Richms, we're pretty much set on the heat recovery ventilation systems because of the benefits for asthmatics and allergy sufferers (as is our daughter).  However, given a dehumidifier would be about 10% of the heat recovery ventilation system price, perhaps we should reconsider.  It's unlikely 'the kids' will remain in the flat for more than a few years, so it's quite a big investment for a relatively short period. 

Aside from being a bit ugly, cumbersome and perhaps a bit noisy, what are the drawbacks of dehumidifiers?  Is the noise something people can get used to sleeping with?

Most importantly, would a dehumidifier help with asthma/allergies at all?

Handle9, thankfully the concrete blocks are lined.  Not sure about wall insulation but figure that the blocks themselves and the lining would be of some insulation benefit  :-)

Amosnz, thanks for the info re the oil heater in your daughter's room.  That's a good bit of knowledge I can pass on to them.  We can definitely see the benefits of the heat recovery systems rather than the standard HRV.  It would be great if we could get a woodburner in there but the place is just too tiny. 

Thanks again to everyone for all your advice.


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  Reply # 1096101 26-Jul-2014 13:21
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I don't sleep with it on. Naturally the bedroom ends up too dry in winter at my place overnight because of the single glazing sucking all the moisture out overnight. I do run it when I have washing over the clothes rack since I don't like to totally finish it in the dryer since the last part takes forever in that.

Before I got the better curtains I actually would leave a bowl of water on the heater to stop the room getting too dry overnight.




Richard rich.ms

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  Reply # 1096120 26-Jul-2014 13:53
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bramwell: ...
Jase, if they run the heat pump with all adjoining doors open it seems to take forever to heat up since the heat pump is too small.
...


Hammerer: ...
The current heat pump sounds like it might be too small to have been properly sized for the living area. They perform more efficiently if they're not running at full power. So it is probably worthwhile to open the doors to the bedrooms and run the heat pump during the day to get better efficiency and raise the background temperature. Then use electric heaters to boost the temperature at night.
...


I think you should reconsider what Jase and I have recommended. Try running the heat pump during the day to raise the base temperature in the entire flat:

 

  • Your heat pump is most efficient when it doesn't have to work hard. That means when there is the smallest temperature difference between inside and outside which usually means during day light.
  • You won't be giving it the difficult task of heating the entire flat from cold. At night, its efficiency drops so it will be unlikely that you get the full output of 3.2 kW. So you can help it out with an electric heater.
  • I regularly turn our heat pump on in the afternoon and open doors to the rest of the house so I raise the temperature to about 18C. Heat transfer through open doorways is rather ineffective because the convection currents tend to recirculate within the room giving little heat transfer to other rooms. We find this even with double doors to our lounge so the longer the heat pump is working then the closer you get to steady state ie hotter in the heat pump room and a little 1-3C colder in adjoining rooms.
  • As an example, my aunt runs her heat pump at 16C all day and night which means that she doesn't get cold if she has to get up in the night. That worked OK without insulation in the ceiling. It works much better in the two months since she has had the ceiling and underfloor insulated. The cost to her while her flat was uninsulated was an extra $50-150 a year over using electric heaters to heat single rooms.
I get bronchial asthma, both temperature-induced and allergic, and I have a lot to do with children that have asthma. I've seen improvements from the smallest changes, even warming a room by as little as 2C can be significant:

 

  • raising the ambient temperature makes it easier to breathe provided it doesn't start you sweating.
  • reducing moisture usually helps - damp really helps dust mites and mould & mildew spores which all cause problems to asthmatics.
  • cleaning bedding and furniture - making sure that it is thoroughly dry. You can also put soft toys, cushions, squabs, pillows, blankets, etc. in the freezer for a few days to kill dust mites.
  • not drying clothes inside because that can be the largest source of moisture and it is often not far behind people exhaling moisture. We started using our electric clothes drier more often because the cost of heating moisture-laden air is not much less than the additional cost of using the drier. Rooms heat up faster and stay warmer longer. We have 6-9 people in our household and do a lot of washing plus I have twenty years of power stats to be able to calculate costs and savings.

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  Reply # 1096145 26-Jul-2014 14:40
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richms: Before I got the better curtains I actually would leave a bowl of water on the heater to stop the room getting too dry overnight.


I don't understand this part, could you explain your thinking? The excessive condensation suggest the room is moist enough.




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