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Evaporative is great except for blisteringly hot days

Kim
Established Contributor

Evaporative is great except for blisteringly hot days

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It's really hot today and we have evaporative cooling installed.  It does a great job until mid-afternoon, and then the challenge of the heat seems too great to keep the house cool. For anything except scorchingly hot days we love the cool, seabreeze feel of evaporative, and having the bi-folds and windows open.

 

We're thinking about installing a split-system in addition to the evaporative, but it feels like an expensive approach to keeping the house cool on those few hottest days of each year.

 

Has anybody else done this, or anything else to help out their evap system when it can't quite handle the blazing heat?

aussiblue
Established Contributor

Re: Evaporative is great... except for blisteringly hot days

In regards to the advice 'If you don't do it already, the trick is to only have open the windows or doors in the area of the house you are using at that time", the problem with this approach is that it can build up the air pressure in the ducts going to those rooms to the extent that the duct walls servicing those rooms blow out and prematurely fail. You really need to have a way for air to escape from any room that is being serviced by a duct. It will however  work in some modern systems  that have small electric motors that remotely close damper at plastic duct junctions so the all air flow and pressure can be removed from the ducts servicing those rooms you want closed off (e.g. https://www.polyaire.com.au/products/fittings/quick-connect-dampers/ ) .

Desi
Newbie

Re: Evaporative is great except for blisteringly hot days

Could you please tell me are you all talking about dry hot days or places like nth Qld where we get extreme high humidity????

 

Sweltering DesI

Jason
Community Manager
Community Manager

Re: Evaporative is great except for blisteringly hot days

Hi @Desi,

 

Is your question directed at the original poster @Kim? If you could provide a little more detail about your question, I'm sure our helpful members would be more than happy to assist. I assume you are interested in installing a new cooling system and are wondering what the community might recommend is the most appropriate for northern Queensland?

 

Welcome to the Workshop community. We are looking forward to reading more about your projects and plans. Please feel free to post anytime you need assistance with anything around the house and garden. We have helpful members sharing advice and inspiration on the site every day. 

 

Jason

 

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JDE
Super Contributor

Re: Evaporative is great except for blisteringly hot days

We live in Tamworth occassional 40+ day in summer. My daughter's house has evap cooling which is ducted. Which is cheaper to run but doesnt cope on supper hot days or humid days. The thing with evap systems is they rely on a change of air and require venting. We put in 2 split systems one in the lounge and one in the bedroom for hotter days. It works well as long as you dont run both at once. Refrigerative systems work best with nil venting.  Typically the evap system is run early in the day or night and then windows closed and the split systems used when too hot. The extraction whirlybirds on the roof have also proven sucessful for us as they greatly reduce the temperature in the roof.

JDE

Re: Evaporative is great... except for blisteringly hot days

Hi @aussiblue  - it has been over 4 years since you commented that you will install the security relief vent in your ceiling.

 

can I please request you to share your experience on whether are you happy with the security relief vent with whirlybird on your roof or it turned out as a disaster?

 

I am thinking of doing the same so would appreciate if you share your experience.

Re: Evaporative is great... except for blisteringly hot days

Welcome to the Bunnings Workshop community @kamranmandhai. It's brilliant to have you join us, and many thanks for your question.

 

Hopefully, @aussiblue can provide us with some feedback on their project. It's been some time since they were active in the discussion, so perhaps you'd like to tell our knowledgeable members a little about what you're hoping to achieve. I trust they'll be full of helpful advice that will have you well on your way to a cooler home during those sweltering summers.

 

You might like to check out this useful Air conditioner buying guide and this best advice article on How can evaporative cooling be more effective?.

 

We look forward to hearing all about your projects and plans around the house and garden and would encourage you to reach out anytime you need assistance or have something to share.

Mitchell

 

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aussiblue
Established Contributor

Re: Evaporative is great... except for blisteringly hot days

Ok, due to health issues, I only got around to fitting them in November last year (2021). I now have  a security relief vents  in almost every room (positioned as far from in the inlet as possible) and in each (2) hallway (so 10 in all) and it is one of the best home improvements I have ever done; the rest of my family love it.

 

It took me a while as I decided to glue fire mesh (similar to this https://www.bunnings.com.au/syneco-810mm-x-2-05m-stainless-steel-insect-screen_p4110616 ) and rodent mesh onto each of the six panels in each security grill (these grills were what I used: https://www.polyaire.com.au/products/grilles/security-relief-grille/ ) to ensure rodents and snakes can't use them as entry points. I have had dugites in the roof space before - probably attracted by the rodents which are in turn I strongly suspect are attracted by my neighbours dog self-feeders, and high had visions of them falling through these new vents into my bed at night..  The fire mesh alone may have been enough, but I also had visions of the rodents eating the glue I had used for the fire mesh so added the rodent mesh (this https://www.bunnings.com.au/whites-90cm-x-5m-x-6-5mm-x-6-5mm-mouse-mesh_p3040081 ) . 

 

It was also hard (at least in my house) in the two smallest of five bedrooms to find a space between the joints to fit them (this tool worked well finding the wooden beams hold the gyprock ceiling panels  https://www.bunnings.com.au/franklin-prosensor-t13-professional-stud-finder_p0117223 ) . So much for standard joist spacing.  In those two cases I fitted door vents (these https://www.bunnings.com.au/haron-635-x-185mm-aluminium-door-relief-vent_p0811178 ) near the bottom of the doors so the air could escape  into the hallway and then through the ceiling security relief grills i had fitted there.

 

The security relief vents really do work extremely well and have kept the temperature in the mid or low 20 degrees C or less in the 40 degree C plus days we have been having. Most days with system on it less than 22 degrees C inside.   I also have 5  of these https://www.bunnings.com.au/brutus-300mm-aluminium-roof-vent-black_p0810900 whirlybird extractors fitted on my tile roof at close to the roof peaks  (3 would probably have been enough) so the air pumped into the ceiling space can escape.  By pumping the cold air into the roof space it gets rid of the hot air that otherwise normally accumulates there greatly increasing the cooling effectiveness of the evaporative air system. 

 

Pushing the air out through the security vents into the attic space also keeps the air around the ducts in the roof space cool and I am sure that also greatly helps the systems effectiveness and efficiency. Indeed, I have read of people in the southern parts of U.S. then finding they could replace the existing foil covered wire wound insulated ducting with sturdier and much longer lasting rigid and semi-rigid steel or aluminium ducting albeit with strapping to address noise issues from the metal ducts moving . This sort of stuff https://www.novaflex.com/productcart/pc/Stainless-Steel-Ducting-Flexible-c61.htm .  I may look at progressively doing the same if I can find similar competitively prices fire resistant flexible stainless steel ducting in the right sizes locally (i.e replacing the existing ducts one or two at a time as they were out).

 

 

In summary, using the security relief vents and whirlybird has greatly increased the efficiency and effectiveness of the evaporative cooling.  Even with the sytem turned off there is usually a cool gentle breeze felt across the floors as the whirlybird draw air out of the room. We now use the system in three stages as needed as follow: 1. off with just a flow of air from the whirlybird extractors, 2. just the pump on so the air drawn out by the whirlybirds is cooled and 3. evap system on. There is the added security bonus of not having to leave any doors or windows open.  As I have found, this also means I no longer hear the noise my neighbour's noisy weekend parties coming through my partially open doors and windows that used to keep me awake and I can come home on a hot day and just immediately turn the air conditioner on without first going around and unlocking doors and window. I am going to use some leftover panelscape panels (this https://www.cassbrothers.com.au/panelscape-bathroom-panels-1800mm) cut to size and covered with rockwool insulation to replace each of the six little panels in each security grill during the winter to draft-proof the house as well as pulling back into place the existing insulation panels that I had to move to fit the security relief grills.  Essentially copying this idea https://evapseal.com.au/ Yes; the downside of these new ceiling vents is that without doing this you would probably almost freeze to death in winter.

Re: Evaporative is great... except for blisteringly hot days

@aussiblue 

 

Thanks heaps for a comprehensive response.

 

Correct me if I am wrong but the security relief vent shuts itself off if there is no positive air flow inside the house (i.e. when the evap is not running). if that is the case, how do you manage to run just using Whirlybird as an extractor? And what is different between Pump only and running evap as normal?

 

I did a DIY thing using this product (https://www.bunnings.com.au/900-x-600mm-3mm-melamine-white-mdf_p0610153) to replicate the "Evapseal" to make the evap vent draught proof in winter. but I don't understand why do you need to make the security vent a draught proof given it got the flap on it.

aussiblue
Established Contributor

Re: Evaporative is great... except for blisteringly hot days

No; I forgot but should have mentioned the plastic cardboard like flaps that are meant as a valve don't work (they don't open when the evap air is on; well not in my house unless the evap air is set to the high setting -  instead of opening the valves in my house on low settings the air as noisily is forced out of the window frame vent slits and other places)  so I simply removed them. The valves plastic cardboard material was simply too stiff to bend and open.  They have changed slightly in their construction since I bought them (they appear they may now have hinges rather than just simple folds in the plastic cardboard like material)  so perhaps they have been improved so they now work as they were meant to. In any event, I believe in summer they work better without these valves allowing air flow even when the evap air is not on. I also suspect with continued use these valves may eventually take a set" at the fold where they are meant to bend and stay open. In any event I consider in conjunction with the whirlybirds, they will work much better without them in summer. There was also a marked drop in air speed of air, measured with the anemometer, coming out of the vents with valves in place so you obviously lose something with energy needed to force these valves open..

 

Note the original cardboard plastic valve bits are designed to be locked closed in winter but I have doubts about the practicability unless Polyaire has changed the design considerably. The whole grill assembly has to be removed to clip them down from above (unless you want to remove roofing or crawl around in the roof space to do it) and I don't think the grill that I bought would survive repeated removal and installation. These grills have spring clips that push into slits in each corner of the grill frame so the revolve down onto the upper surface of the gyprock ceiling sheets as in the photo below.  During installation, and despite my care, two failed as pictured below.  One continued the manufactured split to the frame edge rendering it useless and another broke per the pictures below.  These retaining springs have a a lot of tension and the take some strong fingers and effort to install correctly.  If I had to do this again, I would consider just using some normal refrigerated air grills instead; something like this perhaps https://www.ebay.com.au/itm/122676272747?hash=item1c90135e6b:g:udEAAMXQuCdTgAVW or https://www.metalflex.com.au/product/return-air-grill-380mm-x-510mm-1311708 .  They might also have the advantage of a grill size that would stop, mice, rats and, most importantly to me, baby deadly venomous  snakes getting through without the need for any modification.The origin grill size on the polyaire product is probably small enough to stop rats and mice but not baby dugites. Baby dugites, despite their small size, are as deadly as the adults and dugite appear to like wintering in my roof space so I suspect they are laying their batches of 30 to 40 eggs up there too.

 

Note that since I moved in to my house in Bibra Lake in the early 1980s (it's across the road from the Roe freeway reserve which was native bushland)  I have remove more than 30 dugites from my yard (and seen but been unable to catch several shier and much faster whip snakes - much too fast and evasive for me and my snake bag and hook) and three dugites from inside the house itself. Dugites are much stronger than I once thought and I have observed one juvenile push up the bottom of a sliding screen security door to enter the house and another large adult push up a fiber cement soffit above the aluminium frame of my kitchen window to enter the roof space (something I had difficulty replicating with my hands).  At least with these security grills  installed, I can now leave my sliding glass patio doors shut and I doubt a dugite can lift those heavy doors them to get in.

 

 

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