HRV systems needed for new homes with double glazed windows?

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sqlpro

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#73781 22-Dec-2010 09:25

Hi guys
wondering if you've any advise for me. one of my friends getting HRV system installed and suggesting i should do too. BUT i was under impression that if you've double glazed windows you dont need any such system. am i wrong ?

we never felt dampness in our house. i even tried running dehumidifier the other day in all rooms and it did not collect even 1/2 litre. only place it collected any water was walk in wardrobe.

my friend point is that hamilton has high humidity and may cause asthma if you are not careful. am not worried but we've a 3 yr old and want to make informed decision before taking huge cost installing a system.

your advise appreciated.

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#420290 22-Dec-2010 10:05

What problem are you trying to avoid by installing an HRV?

Humidity does not cause asthma...

freitasm

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#420291 22-Dec-2010 10:07

Humidity makes it harder to keep a house warm - in winter the cold can aggravate asthma.

Humidity makes it easier for mould to grow - which might be related to alergic reactions that in turn can aggravate asthma.

There may be lots more reasons why a dry house is better. I will vote on those two.

sqlpro

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#420293 22-Dec-2010 10:09

wellygary: What problem are you trying to avoid by installing an HRV?

Humidity does not cause asthma...

any possible issues that causes asthama ,allergies at home. those ads on tv say these systems fight all these. currently we dont have any health issues but want make sure that it stays that way.

BUT question is double glazed windows homes need HRV/DVS systems which fight dampness at homes ?
thanks for advise.

trig42

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#420297 22-Dec-2010 10:17

Double glazing or not shouldn't make a difference, it's about airflow.

If you like to have all your doors and windows closed most of the time, then there is more chance that your house will get damp (and therefore, a ventilation system will be benificial, only because it circulates air in your home).

Also, if you south-facing/in a valley/don't get much sun then a ventilation system will be beneficial.

We had one of them (HRV or DVS - don't remember which) come and do their spiel at our place - which is about 10 years old, single glazed but fully insulated. We always leave windows slightly open so there is always airflow - I followed the salesperson around the house with their little moisture meter (like building inspectors use) and there was nowhere in the house that was damp. She had to admit that putting in a ventilation system would be pretty pointless in our house. Also, we used a heat pump for heating in winter - which also dries the air if you do have windows closed.

My sister lives in a house which gets very little sun during winter, and she was having dampness issues. The landlord put in a DVS and those issues have pretty much cleared up - so they are beneficial, just not for everyone.

sqlpro

516 posts

Ultimate Geek

#420302 22-Dec-2010 10:27

trig42: Double glazing or not shouldn't make a difference, it's about airflow.

If you like to have all your doors and windows closed most of the time, then there is more chance that your house will get damp (and therefore, a ventilation system will be benificial, only because it circulates air in your home).

Also, if you south-facing/in a valley/don't get much sun then a ventilation system will be beneficial.

We had one of them (HRV or DVS - don't remember which) come and do their spiel at our place - which is about 10 years old, single glazed but fully insulated. We always leave windows slightly open so there is always airflow - I followed the salesperson around the house with their little moisture meter (like building inspectors use) and there was nowhere in the house that was damp. She had to admit that putting in a ventilation system would be pretty pointless in our house. Also, we used a heat pump for heating in winter - which also dries the air if you do have windows closed.

My sister lives in a house which gets very little sun during winter, and she was having dampness issues. The landlord put in a DVS and those issues have pretty much cleared up - so they are beneficial, just not for everyone.

thanks trig42, i think you answered my question. we get lot of sun into our house (almost impossible sit in the house if we dont have a fan/heat pump :)) so probably we dont need any such system.

Kraven

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#420309 22-Dec-2010 10:33

I'm no expert on this, but based on my own experiences...

The BEST methods of reducing dampness is to remove the sources first, before going to the expense of installing an HRV/DVS or similar system. Common things like don't dry laundry inside, ensure your dryer is vented outside, use extractor fans in bathrooms/kitchens that vent outside, etc.

If you don't have a dampness problem, I'm not sure what benefits such a system is likely to give you.

Nety

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#420320 22-Dec-2010 10:53

As above there is no point if dampness is not an issue which is sounds like it is not in your house. A lot of this comes down to how moisture is handled also mentioned above.

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Jaxson

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#420343 22-Dec-2010 11:30

To specifically address your question you have to think about what each system does.

Double Glazed windows prevent heat travel through them better than single glazed windows. (either heat leaving the house when it's cold outside, or heat entering the house when it's hot outside).

HRV type products take air from outside the house and blow it into the house.

Fundamentally they don't overlap at all, so saying you have double glazed windows doesn't then mean you don't need or do need an air supply fan into your house, if you see what I mean?

If air in the house is warm and humid then this will condense into liquid water on cold surfaces. If you have double glazed windows, and heat your room, the inside window pane of glass will be warmer. This means double glazed windows are less likely to have condensation problems than single glazed windows, (as long as the room is warm). I suspect this is where you have made the link that it is or is not necessary based on having double glazed windows.

HRV systems are useful in newer houses where the whole house is very well sealed shut for insulation purposes. Even then they work better with windows left open a bit to let some air out easily as it is replaced by the new fresh air. Older houses tend to be draughty, which does the same thing and introduces fresh air into the home. HRV systems blow outside air into the home, so when it's 5 degrees outside, you'll be pumping this into your house, or paying extra to heat it a bit with electricity.

Think long and hard before installing such a system, to make sure you need it, are aware of what it actually is and what operating it will actually entail.

SCUBADOO

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#420350 22-Dec-2010 11:38

FWIW

We have a DVS system that was installed in our home before we purchased it.

Our house on the Kapiti coast faces north. We tend to keep it well ventilated by keeping windows open during warm(ish) weather, summer or winter.

Absolutely no condensation with the system DVS on and likewise absolutely no condensation with it turned off for several weeks at a time, summer or winter. Can I tell the difference? - NO!

Our previous house on the Wellington South coast - winter heating was unvented gas = water floods from windows each morning.

A DVS system may have helped, but I will never know.

Take your pick.

mattwnz

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#420438 22-Dec-2010 14:16

Jaxson: To specifically address your question you have to think about what each system does.

Double Glazed windows prevent heat travel through them better than single glazed windows. (either heat leaving the house when it's cold outside, or heat entering the house when it's hot outside).

HRV type products take air from outside the house and blow it into the house.

Fundamentally they don't overlap at all, so saying you have double glazed windows doesn't then mean you don't need or do need an air supply fan into your house, if you see what I mean?

If air in the house is warm and humid then this will condense into liquid water on cold surfaces. If you have double glazed windows, and heat your room, the inside window pane of glass will be warmer. This means double glazed windows are less likely to have condensation problems than single glazed windows, (as long as the room is warm). I suspect this is where you have made the link that it is or is not necessary based on having double glazed windows.

HRV systems are useful in newer houses where the whole house is very well sealed shut for insulation purposes. Even then they work better with windows left open a bit to let some air out easily as it is replaced by the new fresh air. Older houses tend to be draughty, which does the same thing and introduces fresh air into the home. HRV systems blow outside air into the home, so when it's 5 degrees outside, you'll be pumping this into your house, or paying extra to heat it a bit with electricity.

Think long and hard before installing such a system, to make sure you need it, are aware of what it actually is and what operating it will actually entail.

HRV is a 'brand' of ventilation system, but there are lots of other brands too. They actually get the air from the roof space, not the outside. Not sure what they do if you have a skillion roof, but they would probably have to get the air from outside in that case. Other brands do get the air directly from outside.

sqlpro

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#420440 22-Dec-2010 14:20

i think you guys gave me some good direction on this , thank you very much for that.

floydbloke

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#421683 26-Dec-2010 20:54

We are in a very well insulated and sunny, but windy home and HRV systems are all about air flow. We had one installed because we can't open many north facing windows because of the wind and it's made a huge difference as it's not so hot and stuffy anymore. Fresh air is continually circulating throughout the house. Any mould that was present such as in wardrobes has disappeared as has any condensation on the windows. On sunny but cold days it could be 10 degrees outside yet the roof cavity warms up to say 20 degrees. You set your house temp to 20 and the heat from the roof cavity transfers back down into the house. The system takes away any cooking or pet smells, and gives you a great night's sleep as there is no humidity as the air is drier. We have an asthmatic daughter and she has had no asthma since we had it installed 2 years ago.

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robbyp

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#422203 28-Dec-2010 19:50

floydbloke: We are in a very well insulated and sunny, but windy home and HRV systems are all about air flow. We had one installed because we can't open many north facing windows because of the wind and it's made a huge difference as it's not so hot and stuffy anymore. Fresh air is continually circulating throughout the house. Any mould that was present such as in wardrobes has disappeared as has any condensation on the windows. On sunny but cold days it could be 10 degrees outside yet the roof cavity warms up to say 20 degrees. You set your house temp to 20 and the heat from the roof cavity transfers back down into the house. The system takes away any cooking or pet smells, and gives you a great night's sleep as there is no humidity as the air is drier. We have an asthmatic daughter and she has had no asthma since we had it installed 2 years ago.

Do you have any before and after photos and readings, such as humidity and temperature readings? I would be interested in seeing some actual measurements and statistics for these types of systems.

geek4me

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#422777 30-Dec-2010 21:46

We are in a newly built Golden Home for 2 years now. It has double glazing, a heat pump but no HRV system. We have had condensation issues both winters.

The main problem is the double glazing was done (cheaply) without an insulation layer between the outside and the inside metal frames. The cold outside temperature transfers directly to the inside metal causing bad condensation on the metal and inside glass requiring the windows to be wiped dry each winter morning.

Keeping bedroom doors open at night reduced the problem, if closed water would condense and drip from bedroom light fittings.

An HRV would definitely help reduce this condensation as would (more expensive) insulated double glazing in my opinion. Sub standard bathroom heat-light-fan extractor units which do not extract the required volume of damp bathroom air do not help the situation.

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#422797 30-Dec-2010 23:03

I have retrofit double glazing in my bedrooms and living area, a heat pump, and a small ventilation system with outputs in my lounge and kitchen. I've also completely insulated my old house, ceiling walls and floor.

I run the ventilation system in winter to move the stale damp air out of the house, and to bring the warm air from the ceiling cavity into the house. I turn it off at night because I don't like the noise - I have very sensitive hearing and a loudish older system. I keep it turned off on sunny summer days, as it turns the house into a furnace, because I have the cutoff thermostat set too high and i'm too lazy to reset it - it's in the roof.

The double glazing completely eliminated condensation on the windows on all but the very coldest winter days. Before the double glazing I would have puddles of water on my window sills, now I have a light mist on the inside of the double glazing on ultra cold days. Most days it's nothing, but by morning the room does feel a bit moist and the house needs ventilation.

The heat pump makes the whole living and bedroom area warm. It takes a couple of hours to heat the furtherest bedroom, which is around two corners from the heat pump, but it does it. It doesn't reduce moisture at all, it actually increases it, as warm air can hold more moisture than cold air. I don't run the ventilation system at the same time as the heat pump, I figure why pump cold air into the house when i'm trying to heat it, unless there's a lot of people in the house and it's getting stale.

If I were starting fresh i'd get an integrated heat pump and heat recovery ventilation system. The heat pump goes in the roof and heats the whole house, if you switch it on, and it's connected to the ventilation system. If the heat pump is off the ventilation system works without it, putting fresh air into the house. In summer it cools the house using passive cooling, in winter it warms it. I spent a lot of time researching it and Cleanaire was my pick for quality and value.

For you a ventilation system may give you fresher, less moist air that's easier to heat in the winter. If your air quality is good and you don't have moisture it'd be of limited benefit. Having it on in winter could give you more free heat from the sun, plus drying on the air and the walls/floor/etc means less heat is required to heat the place.

If money's tight i'd skip it, but if the expense isn't going to cause you problems then there's no harm.

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