Affect of blinds on solar gains

[Wasted Energy]

Hi all

Here is the scenario; large residential block with some rooms failing TM 52 due to high solar gains. I've remodelled these rooms with internal blinds and hey presto problem solved.

But when I look at these rooms in VistaPro the solar gains are exactly the same with or without blinds although the dry resultant is reduced. And this is being queried by the client.

Now my explanation is that when you add internal blinds to a room the solar flux through the glazing is exactly the same, and therefore the solar gains are the same. But what changes is how those solar gains are transmitted to the dry resultant temperature.

Is this explanation reasonable? And if so how can the beneficial effect of blinds be demonstrated in Vista?

W

[Complex Potential]

Hi Wasted

In my experience the correct implementation of blinds does result in a noticeable drop in solar gain although it is sometimes difficult to demonstrate. I would recommend having two separate models, one with blinds and one without, and then open the results files side by side and check out the annual, monthly and daily profiles overlaid on each other. Also, if you compare the total energy summation for solar in vista rather than just the peaks it might provide a clearer picture.

CP

[Wasted Energy]

Hi CP

Yes when I looked more closely there were differences. And when I summed up the differences I found that there was an average reduction in Solar Gain of 15%. Not much - but enough to cross the line in terms of TM52.

I'm using a variation profile to lower/raise the blinds with the following formula; gt(idn,450,300), and the blinds have an SC = 0.3 and SWRF = 0.6.

Do these figures seem in the ball park to you?

Regards

W

[Complex Potential]

Hi Wasted

The SC and SWRF seem fine but I dont normally control using a formula. My preferred method is to utilise the solar flux thresholds because it then automatically adjusts for varying glazing orientations around the building.

[Wasted Energy]

Thanks for that CP

Turns out the client ain't so keen on blinds anyway and prefers to drop the g-value instead on these particular windows.

W

[RossThompson87]

and the blinds have an SC = 0.3 and SWRF = 0.6.

Do these figures seem in the ball park to you?

Hi Wasted,

Did you actually manage to get these figures from a blinds supplier?

I have never had any luck trying to find these figures. IES did publish some reference figures a while back:

http://www.iesve.com/content/downloadasset_2000 See here table 8.

I haven't seen them promoted recently though.

Ross

[Wasted Energy]

RT87

I think I took the data from;

http://www.arc-ers.co.uk/wp-content/upl ... shades.pdf

W