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29 posts

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# 255582 19-Aug-2019 15:31
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Hi folks

 

I am investigating getting a Dry Living system installed into our old, damp, 60s brick house. It is like an HRV, but the Plus System only takes air from the outside, runs a dehumidifier over it, and then uses a heat exchanger to warm it up before bringing the air into the house. They're a bit more expensive than a Smartvent system at $7,600 installed vs. $4,600 for a Smartvent Evolve 2 + outdoor air unit. However the Smartvent doesn't have a heat exchanger, and only uses outdoor air sometimes.

 

Does anyone have any experience with this system, or experience in the area to know whether this sounds like a good system or not? I like the idea of not bringing in air from the roof cavity, but maybe after the filters it doesn't really matter? Also, we have someone in the house who is allergic to dust mites, does the roof air make this worse?


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  # 2301738 19-Aug-2019 15:43
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You're treating the symptoms, but not the disease,

 

If your house is damp its usually got water coming in outside (from the subfloor) or surrounding dampness, or water from the showers/cooking not being able to get out...

 

- possibly compounded by coldness - although with a brick place you should have  a reasonable level in insulation to start with...

 

 


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  # 2301739 19-Aug-2019 15:54
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You say it is damp house. I would first spend the money on treating the source. Do you have a vapour barrier under the house. Is it fully insulated. Does it have extractor fans in the bathrooms and kitchens. Do you use gas cooking or heating. Does your dryer vent outside. Do you dry your clothes inside. Do you open the windows during the day. Allllll of that would be better spent ticking off with that money first. 

 

Smartvent does come with a heat exchanger add-on, so I wouldn't right them off just yet. Other than that it sounds like a solid system. I'd be interested to find out if it dehumidifies the air coming from outside, or the air it is recirculating from inside.

 

 


 
 
 
 




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  # 2301765 19-Aug-2019 17:22
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Jeeves:

 

You say it is damp house. I would first spend the money on treating the source. Do you have a vapour barrier under the house. Is it fully insulated. Does it have extractor fans in the bathrooms and kitchens. Do you use gas cooking or heating. Does your dryer vent outside. Do you dry your clothes inside. Do you open the windows during the day. Allllll of that would be better spent ticking off with that money first. 

 

 

  • No vapour barrier under house, though I do have the wrap sitting in the garden shed, I should probably get that installed.
  • We added Expol Black insulation to floor and Pink Batts R4.2 to the ceiling
  • Previous owners insulated all walls in house bar one in the dining room (not sure to what standard, but decent enough I think)
  • Extractor fans in bathroom and kitchen
  • No gas cooking or heating, only heat pump and electric stove/oven
  • Dryer is in the garage
  • Don't dry clothes inside
  • Don't open windows much during the day because it's cold (we're in the Waikato, and in a bit of a hollow surrounded by big trees)

Jeeves:

 

I'd be interested to find out if it dehumidifies the air coming from outside, or the air it is recirculating from inside.

 

 

I've sent an email to double check but I assume it must be the air coming from outside, I couldn't imagine what benefit you'd get from dehumidifying the air just before you expel it.


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  # 2301931 19-Aug-2019 19:57
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dantiberian:

 

  • Don't open windows much during the day because it's cold (we're in the Waikato, and in a bit of a hollow surrounded by big trees)

 

maybe so but even an hour will make a noticeable difference in moisture.


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  # 2302011 19-Aug-2019 23:12
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What kind of room temperatures are there inside the house? Do you have a sensor to tell you what the indoors relative humidity % is?

 

 

The vapour barrier is a must. Do look into insulating the wall without insulation. What kind and quantity of glazing does the house have? Many 60s houses' wooden windows constantly leak air.

 

 

The Waikato can be very damp so the outdoors air may be 80 to 100% relative humidity most of the time. That means opening the windows doesn't help much unless the air inside the house is then warmed above the outdoors temperatures.100% humidity air must be warmed by about 10c to halve the relative humidity.

 

 

To kill dust mites the air inside your house must stay below 55% relative humidity every so often.

 

 

It's hard to say whether ventilation or room temperature is the bigger issue.

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  # 2303731 22-Aug-2019 11:59
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When we renovated our house, we installed underfloor insulation and a moisture barrier on the ground. 

 

We also had the floors sanded and polished at the same time (and the gaps between the t&g filled). 

 

The house dried out so much over the next 3 months that our t&g floors have noticable gaps (up to 4mm) between some boards now. 


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  # 2336382 13-Oct-2019 18:43
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Just looked at this for our place as well, the Casa de Cowboy is a pole house and we're building out the basement, meaning the bits that are currently poles will be turned into enclosed living space. "Basement" carries connotations of cold and damp, so I was wondering whether it's worth going with a Dry Living system. Obviously we'll be making it as insulated and damp-proof as possible, but wondering whether the built-in dehumidification in the Dry Living system is worth it as an extra safety measure?

 

 

It's a somewhat unusual way to handle it, pushing dry air in rather than removing moist air, or at least moisture from the air, I'm wondering how well it will deal with the bathroom and laundry that'll be in the basement...

 
 
 
 


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  # 2336385 13-Oct-2019 18:47
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Jeeves:

I'd be interested to find out if it dehumidifies the air coming from outside, or the air it is recirculating from inside.

 

 

It dehumidifies the air coming in from the outside. My concern, see my previous message, is how effective pushing in dry air is vs. extracting moisture. Talked to one of the guys behind it and he said it can get rooms so dry that the paint will crack (if you set it to maximum dryness, which was kinda silly), but I'm wondering whether anyone has any actual experience with it? How much power will it chew getting a room that dry?

 

 

My reason for looking at it is that we'll need to get some sort of forced-air system anyway for the parts of the basement that will be built into the hillside, and if the Dry Living one is a bit more but does a much better job of keeping things dry then that might be the one to go for.

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  # 2336421 13-Oct-2019 20:12
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Reading the website, it doesn't sound like there is a high-efficiency heat exchanger. If there was then they would have some sort of exhaust for air removed from the house.

 

It sounds more like they just mix air from inside and outside inside their box where they dehumidify it before forcing it all back into the house.

 

If that's the case then I'd just put one or more dehumidifiers into my house. Unless it is a modern sealed home then fresh air will be getting in anyway.


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  # 2336454 13-Oct-2019 20:59
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A standard heat recovery ventilation system could probably do much the same job. It would bring fresh dry air in, warm it with the stale outgoing air, and it would slowly dry the place out. I've never heard of one with a dehumidifier inline.


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  # 2336460 13-Oct-2019 21:24
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Jase2985:

 

dantiberian:

 

  • Don't open windows much during the day because it's cold (we're in the Waikato, and in a bit of a hollow surrounded by big trees)

 

maybe so but even an hour will make a noticeable difference in moisture.

 

 

 

 

100%. Even in Dunedin in the middle of winter I open windows when not home for the day. It's a whole lot easier and cheaper to heat a dry home than a damp one. 


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  # 2336473 13-Oct-2019 22:04
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How many people in your household? People expire quite a lot of moisture per day. I forget what the average amount is supposed to be.


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  # 2336484 14-Oct-2019 00:59
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DarthKermit:

 

How many people in your household? People expire quite a lot of moisture per day. I forget what the average amount is supposed to be.

 

 

If my house was always damp then I'd be checking other things first:

 

  • the ground under the house if it has suspended floors.
  • natural gas heaters.
  • the ventilation of kitchen, bathroom and laundry particularly with clothes dryers, baths and showers.

In our house with six adults we dry it out through winter by opening windows, venting showers, and overnight dehumidifying 2-4 litres a day.

 

Under extreme load we can sweat up to two litres an hour but I expect that we only expire about 20-30ml an hour a lot of the time. Say 250-500ml a day but I have seen figures as high as a 1,000ml a day. Heavy exercise can increase it to 100ml an hour but we don't usually do that at home.

 

However, some sources are clearly unreliable. For example, the Level - a BRANZ website on sustainable building which is usually a good source - gets it wrong here: http://www.level.org.nz/passive-design/controlling-indoor-air-quality/humidity-and-condensation/. They say "A person exhales approximately 200 millilitres of water vapour per hour while awake and approximately 20 millilitres of water vapour per hour during sleep." This would be about about 3,200ml for 16 hours awake and 160ml for 8 hours asleep. A total of over 3 litres a day is clearly incorrect.

 

Anyway, how much water we expire is dependent upon environmental humidity as we lose more when it is dry than when it is humid. So if my house is damp then I expire less water. If my house is dry then I might expire twice as much.

 

 


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  # 2336491 14-Oct-2019 03:06
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My house has a hell of a lot of rising damp under it. I am gradually lining all of the bare ground with overlapping sheets of corflute. I've got over a third done now and it's making a difference.


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