Ventilation - summer kit. Any benefits?

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Starina

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#280331 9-Dec-2020 11:42

Hi,

Does anyone have a 'summer kit' installed for the Positive Pressure ventilation system? Will it help to reduce the temperature in the room?

Summer kit is a separate branch for the ventilation that takes air from the outside, not from under the roof.

Price is not an issue, I just need an extra motorized Y valve, filter and a grill outside. Not really expensive. But before I make a hole in the wall under the roof, I want to be sure that it worth it.

During the last couple of days under-the-roof temperature was 40-50 degrees. Temperature in the upstairs bedrooms reached 33 degrees at 5pm. Quite uncomfortable. When the roof cooled down a bit, I turned on the ventilation to the max speed and the temperature was around 28 degrees in a couple of hours - it was ok.

During the day outside temperature is 23-24 degrees.

My point is:

The sun heats the roof, walls, curtains, so the air inside becomes hot because of these things. Insulation helps, but not a lot.

If during this sunny time I bring 24-degrees outside air, it should help a lot. In the evening outside temperature reduces faster then the house cools down, so should be even better.

Any thoughts?

PS heat pump/air conditioner is not an option for us for now.

Jase2985

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#2618619 9-Dec-2020 13:08

it may help but not as much as you think.

Handsomedan

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#2618620 9-Dec-2020 13:09

We decided against it and went with the traditional heat pump options.

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jasonbug

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#2618634 9-Dec-2020 13:25

Starina:

If during this sunny time I bring 24-degrees outside air, it should help a lot. In the evening outside temperature reduces faster then the house cools down, so should be even better.

Any thoughts?

If you want to bring in outside air, can you not just open a few windows?

Starina

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#2618642 9-Dec-2020 13:35

Thank you for your replies.

Jase2985:

it may help but not as much as you think.

What can be done to increase the efficiency?

If we are taking numbers: outside 23, inside 33, will I get 28 if I run it all day long?

Handsomedan:

We decided against it and went with the traditional heat pump options.

May I ask why?

Starina

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#2618643 9-Dec-2020 13:36

jasonbug:

If you want to bring in outside air, can you not just open a few windows?

It helps if there is a wind outside. Otherwise it's useless and we need to open all windows, put a fan near the window.

I would like to have this thing automated the same way as the ventilation and the heating.

Jase2985

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#2618644 9-Dec-2020 13:43

Starina:

Thank you for your replies.

What can be done to increase the efficiency?

If we are taking numbers: outside 23, inside 33, will I get 28 if I run it all day long?

if there is no added heat from the sun it will get the inside down to 23 degrees. and that would be at night but you have the sun adding extra kw's of heat thats then soaked into the furniture/walls of the house which also has to be cooled. so your small input of cool air will not make much difference in the scheme of things. its just going to stop the ventilation system sucking in hot air over summer. my system turns its fan off over 21 degrees in the summer.

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Starina

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#2618681 9-Dec-2020 14:31

Jase2985:

if there is no added heat from the sun it will get the inside down to 23 degrees. and that would be at night but you have the sun adding extra kw's of heat thats then soaked into the furniture/walls of the house which also has to be cooled. so your small input of cool air will not make much difference in the scheme of things. its just going to stop the ventilation system sucking in hot air over summer. my system turns its fan off over 21 degrees in the summer.

Makes sense. This is what I was afraid of - the only way to check the efficiency is to make it and watch it :)

I have one more option in mind: suck all hot air out of the rooms, so basically reverse the ventilation and let the room to be filled with air from somewhere else.

In this case the hot air near the ceiling will be sucked out and won't heat the incoming air as in the first option.

Can it be more efficient?

As for the hardware - I am going to replace my AC fan to EC fan anyway to be able to change the speed smoothly from 0 to 100%, so I will have my existing fan as an extra and I will be able to use is as a reverse one.

Cheers

timmmay

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#2618728 9-Dec-2020 14:46

I don't take any air from the roof cavity in my very old house. The ceiling cavity is really dirty, mouse droppings, multiple types of insulation, old building paper. I used to have an intake with a basic sock filter and it was black after 6 months, and it made the inside of the house smell funny. In winter it gave us a small boost using air from the ceiling cavity - from memory it might have been a couple of degrees at best. We have only two outlets, into the lounge and kitchen, not directly into bedrooms, so this might be different from your situation. I suspect if vents are in bedrooms it will be quite a bit more effective.

I now take all the air from the outside, through HEPA and charcoal filters. I did the change myself, filter $120, ducting can't remember maybe $30, outside grill $20. The fan runs at half speed to keep noise down, but I'll probably turn it back up when I get around to it.

It doesn't make all that much difference to the inside temperature if the inside temperature is extreme. We have one room that gets HEAPS of sun and can get to 35 degrees in summer easy, I think windows cracked open and ventilation system with air from outside might take it down a few degrees at most. A heat pump / air conditioner is required to drop the temperature much, and it does it really quickly. However, at night if it's say 12 degrees outside and 24 degrees inside it does drop the inside temperature well enough. We use a Kasa WiFi timer to run the ventilation system morning and evening in summer, and afternoon in winter.

Summary (TLDR): I think outside air could help lower your bedroom temperatures if there's a significant differential, and it will prevent it heating the rooms up so much, but I suspect it won't be as effective as you might like unless you're careful with times the system is on. You could consider getting all your air from outside and none from the roof cavity, it will help summer temps a bit and won't really make all that much difference in winter temps in my experience.

Handsomedan

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#2618743 9-Dec-2020 15:18

Starina:

Handsomedan:

We decided against it and went with the traditional heat pump options.

May I ask why?

For all the reasons noted above - basically, you can't efficiently cool a house with outside warm air when the stored heat in flooring, walls and furnishings is being radiated out into the rooms at a faster rate.

Also - the air simply isn't cool enough to make a difference.

A Heat Pump cools the air with refrigerated air and cools the house down more efficiently and much, much quicker.

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Starina

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#2618744 9-Dec-2020 15:18

timmmay:

I don't take any air from the roof cavity in my very old house. The ceiling cavity is really dirty, mouse droppings, multiple types of insulation, old building paper. I used to have an intake with a basic sock filter and it was black after 6 months, and it made the inside of the house smell funny. In winter it gave us a small boost using air from the ceiling cavity - from memory it might have been a couple of degrees at best. We have only two outlets, into the lounge and kitchen, not directly into bedrooms, so this might be different from your situation. I suspect if vents are in bedrooms it will be quite a bit more effective.

I now take all the air from the outside, through HEPA and charcoal filters. I did the change myself, filter $120, ducting can't remember maybe $30, outside grill $20. The fan runs at half speed to keep noise down, but I'll probably turn it back up when I get around to it.

It doesn't make all that much difference to the inside temperature if the inside temperature is extreme. We have one room that gets HEAPS of sun and can get to 35 degrees in summer easy, I think windows cracked open and ventilation system with air from outside might take it down a few degrees at most. A heat pump / air conditioner is required to drop the temperature much, and it does it really quickly. However, at night if it's say 12 degrees outside and 24 degrees inside it does drop the inside temperature well enough. We use a Kasa WiFi timer to run the ventilation system morning and evening in summer, and afternoon in winter.

Summary (TLDR): I think outside air could help lower your bedroom temperatures if there's a significant differential, and it will prevent it heating the rooms up so much, but I suspect it won't be as effective as you might like unless you're careful with times the system is on. You could consider getting all your air from outside and none from the roof cavity, it will help summer temps a bit and won't really make all that much difference in winter temps in my experience.

Thank you for the detailed description.

We have outlets in each room and it really helps with crying windows during the winter. No need to use dehumidifier at all. I also installed valves for each room to be able to blow the air where it's needed (no need to cool down the living room if it's dew point is below the outside temperature).

A few more points: what HEPA filter have you used and what outside grill have you installed?

I have ducting leftover that I will use and my existing charcoal filter. I will install Y branch for the outside air intake between the sock filter and charcoal filter. Yes, there is a possibility that I will stop using under the roof intake if the result is the same.

timmmay

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#2618866 9-Dec-2020 19:56

Starina:

Thank you for the detailed description.

We have outlets in each room and it really helps with crying windows during the winter. No need to use dehumidifier at all. I also installed valves for each room to be able to blow the air where it's needed (no need to cool down the living room if it's dew point is below the outside temperature).

A few more points: what HEPA filter have you used and what outside grill have you installed?

I have ducting leftover that I will use and my existing charcoal filter. I will install Y branch for the outside air intake between the sock filter and charcoal filter. Yes, there is a possibility that I will stop using under the roof intake if the result is the same.

If I had put the system in I'd have done each room, but it was here when I got the house. It doesn't really help with wet windows, but double glazing solved that problem, and it does clear the moisture out of the house quite effectively. If I get the ducted heat pump system that'll increase airflow which will further help. I don't really want to pump cold air through the house to keep it dry.

I got this filter, they added an activated charcoal layer to it for me, cost another $20 or so. Good information and service from filter specialists. Not sure what grill I got, some 200mm one but I don't know what exactly, I got it from a trade outlet.