Ventilation system or replacement heat pump?

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Smix

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#236298 27-May-2018 17:54

Hey Team,

My wife and I welcomed our first child into the world a couple of weeks back and I'm in a bit of a conundrum at the moment as to whether to replace my very old heatpump (came with the place I bought 5 years ago, and looked very old then, and seems to struggle at maintaining a good temperature) or get a Smartvent + heat recovery system. Financially it is only one or the other with a budget of ~5k. We live in a '60s ~100sqm single level house; it is not airtight. I'm thinking an 8kw airpump with a view of it reaching the other bedrooms.

We do get a fair bit of condensation, however, with the heatpump constantly on in the lounge, it hasn't really been an issue so far. The same with our master bedroom (where her bassinet is) since I installed a eco panel (I guess it's moving air around?)

Would be great to get some feedback as to which way round you'd go, and why.

Thanks!

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#2023515 27-May-2018 18:31

Not much point in forced ventilation in a building that isn't airtight, as it already has natural ventilation. The point of ventilation is replacing stale air that has high moisture content with fresher/dryer air from outside. If that is occurring naturally through existing air movement, no point in paying more to do the same.

Probably better to replace the existing heat pump, or consider two smaller ones if there is more than one area you are wanting to heat. Upgrading insulation is also useful and could be a good idea to put some money in to.

irongarment

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#2023571 27-May-2018 20:20

Would it be cost-effective to have the existing heat pump checked/serviced? Perhaps the refrigerant could be replaced or topped-up?

timmmay

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#2023575 27-May-2018 20:26

Congratulations :) Fun times, hope you're getting some sleep!

I agree with RunningMan. If the house leaks a little air, and you can open the windows occasionally, I think go for the new heat pump or two new smaller heat pumps.

If you don't have a good level of ceiling insulation, add some / some more. It's cheap and can make a huge difference to the warmth. My house is quite old and had none when I first purchased it. I added loose fill wool and it made a good difference, especially when I added a heat pump. A year or two later the wool was compacting so I added pink batts, which made another big difference. Underfloor plastic and insulation made the house much less damp and smell better, but not a lot warmer, given we have underlay and carpet. Wall insulation made some difference. Double glazing made a good difference, and got rid of condensation.

The house had a really small cheap ventilation system when I bought it, just a fan with an outlet really, I modified it to get fresh air rather than ceiling cavity air which smelled, and I run it on a $12 Miter Ten timer. In winter it runs 11am - 3pm, plus 15 minutes at around 7pm, 10pm and 6am. Works well. In summer I run it early morning and late evening, so it doesn't bring really warm air in.

Jaxson

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#2023577 27-May-2018 20:32

I'd query how the heat from the oversized heat pump is going to reach the other rooms?

Heat pumps are just efficient fan heaters, so if you build expectations around that you won't be disappointed.

Condensation comes from warm humid air touching cold surfaces, so opening the windows/doors a few times a day will really help to move that moist air out of the house.
Or run a dehumidifier, or get a ventilation system.

A heat pump will provide heating in winter, cooling in summer, in the room it's in.

Both have different functions.

scuwp

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#2023579 27-May-2018 20:35

2 completely different things. One is for ventilation, the other heating. You can’t have ‘heat recovery’ when there is no heat anywhere to begin with. No point having a. Dry house if you are freezing, my vote is go for warmth first, then look at what you can do regarding the condensation later

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Aredwood

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#2023586 27-May-2018 20:48

What is the make and model of the heatpump? Download a service manual for it. There should be a procedure for doing a capacity test on it. Where you put it into forced high operation. Measure the temperature of the air being drawn into and discharged from the indoor unit. And check that the temp rise is within spec. Also so you can check what it's rated COP figure is. And see if a newer heatpump will give a worthwhile gain in efficiency or not. If you close all of the internal doors, does the lounge heatpump heat the lounge?

A single room heatpump is not designed to heat a whole house. Sure, some people can get away with doing so in a well insulated house. But even then, the whole house won't be an even temperature.

I reckon get a 2nd heatpump installed in the master bedroom. You can keep baby in there as well overnight. And the lounge heatpump will then have less work to do. Also smaller heatpumps are both cheaper and more efficient than larger models.

Also a ventilation system cannot lower the indoor moisture levels anymore than whatever the outdoor moisture levels are. This is especially important if your property is surrounded by trees and /or get little sun. It will always be damp outside, so the only way to reduce damp inside is aircon during summer and a dehumidifier + extra heating if needed during winter.

And consider a dehumidifier instead of the panel heater. As a dehumidifier gives you 0.6KW/Hr of free heating for every litre of water that it removes from the air. Due to the latent heat of water.

Is the condensation on the Windows or window frames? If they get cold enough, you will still get condensation even if you have low indoor humidity. Solution is to get double glazing.

edited to add

And a warm house is going to leak more air than a poorly heated house. Due to how convection currents work. So once you get the heating sorted. You will get more ventilation wether or not you want it.

Definitely a vote for a heatpump from me.

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timmmay

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#2023596 27-May-2018 21:14

Jaxson:

A heat pump will provide heating in winter, cooling in summer, in the room it's in.

The heat pump in our lounge also heats the three bedrooms, even though it doesn't blow directly into them - it has to go around at least one corner. We do have the heating on from 5am until 10pm though, and it's a fairly well insulated older house.

I find heat easily goes around one corner or through one doorway, but not much more. The exception is our lounge entrance is huge, and the hall very wide, heat goes around a corner down the hall, then around another corner (180 degrees from the heat pump) into the room if given enough time.

We still use oil heaters in the bedrooms at night as the doors are closed. I wouldn't want a heat pump in the bedroom, they're too loud. Ducted, maybe.

More NZ houses should have central heating, ideally heating and cooling.

Smix

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#2023609 27-May-2018 21:38

Awesome, thanks everyone for the great advice - sounds like I should engage with an installer around options for a couple of units instead of a larger one...wasn't aware that that simply getting a bigger one wouldn't heat (to a certain extent) the rest of the house. Completely understand that they're two different things but my conundrum centres around 'what is the better option?' I get work discounts from Noel Leeming and from the couple I queried, I was looking at roughly 20% off the ~$3k Fujitsu models.

We got our bathroom renovated a couple of months back and the sparky said there's "a crap load" of insulation in the ceilings. We also have underfloor but nothing in the walls. Unfortunately double glazing the entire house is cost-prohibitive, and as this is my first home I am hesitant to draw any more funds from my mortgage (as I already have for the bathroom) i.e it's not my forever home. We are looking at selling in the next 1-2 years.

@Aredwood and @irongarment I'll look into the make model and see what I can do. It does heat the lounge, but doesn't seem to be anywhere near what the temperature on the remote says. Once I've had the installer in I'll also weigh up whether I get a smaller unit in the master and get a service on the lounge unit, or just biting the bullet and doing both at once. Thanks also for the advice regarding the dehumidifier.

@timmmay I don't even know what sleep is anymore!!!

Aredwood

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#2023636 27-May-2018 22:12

Since money is an issue, just get a bedroom heatpump for now. And check the COP figures before you buy. The newest models use R32 gas, while the older technology ones use R410. In the 2.5KW output class, you can get heatpumps with a COP of 5 or close to it. Since it will be replacing an electric resistance heater, the heatpump will be 5x more efficient.

Let's say that your current lounge heatpump has a COP of 2.5, and you replace it with one that has a COP of say 3.8 (unlikely to get much more than that for a large heatpump). The new heatpump will only be 1.52X more efficient than the old one. So nowhere near as cost effective to upgrade it. Of course it is still a good idea to go for the best efficiency for a new install. Or if your old heatpump has failed and can't be easily repaired.

No point in trying to save money on running costs, if you will instead be spending the saving on higher interest payments.

There should be a sticker on the outdoor unit with the make and model numbers on it. Which will also have the heating and cooling capacity listed as well. Google should be able to find a manual that will have the COP in it.

timmmay

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#2023693 28-May-2018 05:40

A key tip for a heat pump when you have a child, imho, is to leave it running rather than turning it on and off. Just turn it down when you don't need it, maybe to 19 or 20. We had to 21 or 22, 18 or 19 when we're out. House feels much warmer and if it's insulated cost difference not huge.

Double glazing good but unless it has leaky Windows it's not like it'll suddenly be super warm.

Hammerer

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#2023704 28-May-2018 08:03

The state still provides subsidies towards heat pumps and insulation which will help your money go a lot further.

https://www.energywise.govt.nz/funding-and-support/

+1 for insulation which almost always has a positive financial benefit.

+1 for a dehumidifier instead all those heaters (whether fan, panel, radiant, eco, etc) that have no additional efficiency (unlike heat pumps).

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timmmay

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#2023706 28-May-2018 08:08

I'm not sure that a dehumidifier is a great investment. Yes they reduce moisture which makes it cheaper to heat the place (a little), but IMHO if there's enough of a problem to need one it's better to put in a long term solution, such as extractors in bathrooms and kitchens, plastic under floor to stop rising damp, and eventually a ventilation system if required.

mdf

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#2023786 28-May-2018 10:08

Congratulations! It's an amazing time.

I tend to come down on the side of resolving dampness first. You can then heat much more cost effectively. We were in a similar position to you a while back. Once we dried out our home, we got more than enough heat out of a small oil column overnight to keep bubs room at a perfect temperature (we used it with a Heatermate).

Yes a heat pump is much more cost effective to run and pays for itself over the long term. But it sounds like you might sell soon, so it is worthwhile doing your sums. If your extra power bill is only $500-$1000 more (and that's a fair bit of power for keeping one bedroom at a comfortable temperature for sleeping), then it's not worth the extra investment for heat pumping. Non-fan circulated heat (e.g. panel, oil column, micathermic) might be better at night too, since there's no noise or draughts.

We did the de-deamping via DVS and underfloor expol insulation, and I have to say, I initially thought we'd bought a complete lemon. 6 weeks in no difference. But then about week 7 noticed a massive difference.

Consumer is big on dehumidifiers at the moment. The way they work means that you get "free" heat in addition to removing moisture, even with a non-heated model. I'm not sure I'd want one running all night in a kids room though. You might end up making a bit of a rod for your own back if kiddo can only get to sleep accompanied by white noise.

As an aside, I'm really not sure the country has it's policy settings around new borns right. We went through a similar thing - old draughty damp first home, mortgage, a new born, and down to one income. Would have been great to have a bit more financial flexibility then, even if we ended up paying more later. But well and truly off topic.

Hammerer

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#2023953 28-May-2018 13:52

timmmay:

I'm not sure that a dehumidifier is a great investment. Yes they reduce moisture which makes it cheaper to heat the place (a little), but IMHO if there's enough of a problem to need one it's better to put in a long term solution, such as extractors in bathrooms and kitchens, plastic under floor to stop rising damp, and eventually a ventilation system if required.

A dehumidifier can be justified in cold houses even without what would normally be called a damp problem. @Smix seemed to have a localised heating issue with his baby so a low-cost localised solution is likely to be useful (and better than an "eco" heater).

It costs a lot to heat the moisture in the air and other contents of a house. Dehumidifiers allow windows to be kept closed without an increase in humidity because they can remove the moisture that we exhale and perspire. One of my kids uses a dessicant dehumidifier in their flat and we can easily tell the difference between the rooms where it is used and those where it is not.

I'd recommend dessicant dehumidifiers which function at the same rate down to 0C. The much more common compressor-based systems work much better with humidity at temperatures above 20C and much less effective at temperatures approaching 0C. You can find research that describes such issues, e.g. PDF on Domestic dehumidifiers in cool NZ conditions.

Dehumidifiers improve the efficiency of heating your house because their waste product is heat. So a dehumidifier can produce the same amount of heat as a fan heater at the same cost but it is also reducing the heat (and electicity and therefore running cost) required to achieve the same ambient temperature.

How much does it reduce heating costs? One-off heating of 1 litre of water by 1C takes .001172 kWh. That doesn't seem much but over 24 hours assuming a temperature drop of 1C per hour without heating then it would only take 3-4 days to save a kWh.

If my Goldair GW330 dehumidifier runs continuously and removes 4 litres a day (it can get up to 8) then it would take less than a day to save 1kWh of heating. At 25c/kWh for 100 days a year then I'd save about $25-50 a year on a heating spend of $390 resulting in a 6-13% saving. That's not too bad on a $250-300 sale purchase. Plus that's only to maintain 1C/hour of heat loss. In practice, winter heat losses are usually much higher than that.

timmmay

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#2023970 28-May-2018 14:38

How do those numbers work out given you have to buy and run the dehumidifier? They probably last what, five years?

With a baby in the house you don't really want to heat one room, you want the whole house to be warm - whichever rooms they might go in.

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