Tuesday, June 30, 2015

Keeping warm - the ventilation edition

It's been a bit quiet around here as I'm struck down with some kind of horrible lergy - but I did manage a bit of fossicking around in the attic today before I crawled back into bed - you know how when you're sick the first dose of paracetamol often makes you think you're actually okay until you get knocked off your perch mid-morning? So anyway, no photos or real progress to speak of but we've been learning lots about heating and ventilation so I thought I'd share a bit about the latter.

Our house came equipped with two HRV systems. I know this will excite some people - and perhaps in some houses HRV systems are worth having, but I am not sold. Ventilation is good, yes, but several thousand dollars is a big outlay for something that only somewhat dries out the air.

That's a bit beside the point when someone has already put the systems in, though, so we thought we'd give it a whirl. Well, we've been here for two months now, and used the HRVs for the first month (maybe a bit more) while we worked out what to do about heating (there were two heat pumps, but they only heated the rooms they're in, leaving the rest of the house pretty cold).

We've now decided on our heating solution (a reasonably uncommon option for Kiwis - ducted gas central heating - more on that soon as we're in the process of installing the ducting ourselves) and have had a bunch of electrical work done, including having the HRVs removed. Have we noticed a difference? Not really.

We're well aware that ventilation is very important for a healthy home - and lacking in many NZ houses, probably mainly because they feel so cold - but there are other ways to achieve that.

The best way to ventilate, and cheapest by a long shot, is to throw open the windows - as many as possible, in particular those which will catch the cross wind - for 10-30 minutes once a day. Yep, those minutes will be a bit chilly in winter, but a dry house is healthier and easier to heat. Once you've closed 'em up again crank up your heating and it'll warm back up in no time.

If your house is particularly damp (i.e. if you notice a lot of condensation on the windows or walls) you might need to take more targeted action.

The first thing is to avoid putting moisture into the air if possible. Just breathing adds some moisture but don't stop doing that! But there are three main culprits, all of which are reasonably easily solved:
1. Cooking 
Make sure you have a good rangehood over your hob (and that you use it!), and keep lids on pots as much as possible when cooking.
2. Showers
Install a fan in your bathroom if there's not one already - if possible add it to the same circuit as the lights with a delay timer so it runs for a while to clear steam after a bath or shower.
3. Drying clothes
If possible, dry your clothes outside on the line. If you have a dryer, duct it! This is pretty easy to do - you can buy ducting kits from hardware stores and appliance stores, add a couple of hours of your time (or pay a handyman if you're able) and you're all sorted. Here's the bit I only learned recently - if you can't dry your clothes on the line outside you are better off putting them into a ducted dryer than hanging them on an airer inside. You'll likely use more energy getting the water out of your house than you would have done running the dryer.

The small droplet symbol on the
left shows it's on the right mode
Okay - got prevention covered but still damp inside? If you have a heat pump, try running it on the dehumidifying mode for a few hours next time you're out. This only works when it's cooling so it will reduce the temperature, but does an okay job at removing moisture at a pretty low cost. In our old house we did this for about three hours once every couple of weeks in winter, which was enough for us (we actually probably wouldn't have needed to do that I'd learnt the bolded bit above about the dryer a bit sooner).

Freestanding dehumidifiers are even better at drawing out the moisture, so if you're really struggling to keep the walls dry, buying or borrowing one of those and moving it around the rooms of your house should do the trick.

By all means if these things don't solve your problems maybe look into a ducted ventilation system - but please try the cheaper things first! You might be surprised. :-)

Back to our disaster house new home - there was no extraction at all in the kitchen when we moved in, and no outdoor clothesline or dryer ducting. So I'm thinking the previous owner may have jumped the gun a little on the HRVs... Oh, and there is a little moisture issue at the back of the house where the back wall of the laundry is actually the concrete retaining wall - that one will be a bigger problem for us to solve a wee way down the road... Not looking forward to that!

Have you lived in a horribly damp house? Do you have any tips to add?


  1. I'll be very interested to hear about your ducted gas central heating experiences. Certainly seems the way to go for a retro-fit, but will be interesting to see some hard numbers on upfront and continuous costs.

    1. We're interested (and very hopeful!) to see how well it works. It won't be up and running until the middle of the month as the gas line hasn't been run yet but stay tuned... :-)

  2. Love hearing about how your going , I'm surprised you didnt use the HRVs ducting system and just replace the HRV with a heat ex changer . We run a balanced air system with a Zanaderair unit with solid ducting as it lasts longer and has better efficiency because its smooth not ribbed .But we have a very well sealed house , the unit takes the musty moist air out keeps the heat from the air and mixes it with fresh air and back into all the rooms .We are vents placed strategically through the house , extractor vents in bathrooms and toilets , kitchen with ""turbo" buttons you can push for a 20 min faster fan speed And in lounge /bedrooms we have supply vents . In my craft room i have both excavator vent and supply so when im painting with stinky oils i push the turbo button and it sucks the stinky air out and fresh air in . Its great , i have never liked the HRVs , i get the whole positive pressure thing in old houses for sure but taking the "warm" air from the roof space and putting it into the house but but if your moving so many cubic meters of air an hour in winter .. the air wouldn't be so warm after a while and all the while pushing your warm out out all the gaps of the house and $7000 for a fan a filter and ducting for the pleasure not to mention if you don't have a house with long iron roofing ... sheesh ! No thanks :) In our old house we put polythene under the house(it was ring foundation and pile) Batts in the ceiling and a Weiss heat transfer kits running the heat from the log fire into the bedrooms and we also had a small heat pump for when it wasnt too cold made all the difference .Where are you in the country though Welly ? Ps the floors look fab , i miss my Remu floors .

    1. Hmm, yeah, the balanced ones make more sense, and maybe work better in new houses where the house is warmer to start with... I am really interested in passive heating but in a 90 year old bungalow there isn't much we can do (we will be putting a north-facing window in eventually, which will help!). Did you look into that at all with your new place? Do you have any other heating?

      We were hoping to reuse a fair bit of the ducting but it's not insulated so there would be too much loss, and actually the ducting hasn't been ideally installed and the vents aren't very well placed anyway. And there are only half as many ducts as we need. Reusing was our starting point but instead we're installing new ones ourselves for a better result but still a bit less spendy than the gasfitters doing all the work. Solid ducting does sound better but again the $$$ come into play, unfortunately there are a few other things we need to cover as well. I wish the previous owner had knocked $7k off the purchase price and not given us the HRVs but what are you going to do? ;-)

      Polythene under the accessible bits of the house, some underfloor insulation as well, and a top up of the batts in the ceiling are firmly on our to-do list, too... Maybe I should put a progress page up!

  3. I used to work advising residents on how to keep warm and dry during winter. I agree with all of your tips and would also add keep the bathroom door closed after showering.

    While I was in NZ over Christmas a friend stayed in my flat. When I got back it was very damp (water was pooling on my skirting boards!), but I still haven't figured out why. I think it was a combination of winter, drying laundry indoors (I used to only dry it in the kitchen with the window open on a safety latch), turning the bathroom fan off too early and leaving the bathroom door open after showering, but I haven't managed to replicate it!

    The worst damp has come from using a wallpaper steamer to rid my flat of woodchip wallpaper. My place is a 1970-built lower maisonette in a terrace. It's above a garage so was definitely prone to damp from below, but I put down damp proof and insulating underlay before laying the flooring. It's much warmer now.

    I keep the kitchen door open when I'm cooking, and the window, as I don't have any extraction. I am going to put a hood in when I renovate the kitchen but it will have to be recirculating unfortunately as I'm planning on open shelves instead of wall cabinets, so there will be nowhere to hide the ducting! I'd also need planning permission to make a hole in the wall.

    My heating is gas but cooking electric. Gas hobs generate moisture. I'm going to go for induction when I get my kitchen done.

    I dry laundry inside, when the scaffolding is off my block I'll dry as much as I can on the balcony.

    1. Oh yes, hadn't thought of gas cooking but of course it would generate moisture too... We love induction anyway and have our new hob in a box waiting to be installed. :-)