Continuous Diffuser - Manufacturer

[smb4050]

I'm a structural engineer looking for information to help a client on a problem they have outside my area of expertise, so forgive my invasion of the ME forum. The problem is HVAC registers are discharging onto insulated glass units causing the seals to fail prematurely. The attached photos are from 3 or 4 years ago, but show the situation. Since the these pictures were taken the vertical, or lower glass units have been replaced. Some already have condensation between the glass panes or even have interior panes cracked due to the thermal stress. The window manufacturer isn't standing behind the warranty because the original purchaser, the contractor, is no longer in business.

My question is does anyone know of a diffuser manufacturer who may make a deflector so the conditioned air won't blow directly on the glass? Any other suggestions? Thanks, smb

 

[QualityTime]

Can the existing diffuser be adjusted to blow at a different angle?

 

[smb4050]

Thanks for the reply. No they're fixed. The only other option is to purchase new grilles, but I'm not sure that will keep the air off the glass to prevent the fogging or glass from breaking.

 

[DRWeig]

I'd get with my favorite sheet metal shop and have 'em make me a deflector, then finish it to match existing... Shouldn't be too expensive, probably lots less than changing diffusers.

Good on ya,

Goober Dave

 

[tys90]

How did you determine that the air blowing on the window was the problem?

 

[Compositepro]

The whole point of insulated glass is to have low low heat transfer. This means that they should be designed for a large temperature difference between inside and outside. I think you have defective windows.

 

[smb4050]

Thanks everyone for the input and thoughts. Good question about how we determined the air blowing on the window is the problem. The answer is the window manufacturer who is also now saying the warranty isn't valid. We have discussed the posiblitiy of defective windows. What engineering field covers insulated glass failures? Any idea what ANSI or ASTM standard covers insulated glass? Thanks, smb

 

[tys90]

Get the manufacturer to explain how the air is causing the problem in writing. I would even venture to say that as long as the airflow is warm it's mitigating the problem.

 

[smb4050]

I think you're correct. My guess is there are industry and/or ASTM standards the units should meet and the units can be tested to see if they meet these standards. Now I need to find out what they are and who tests them.

 

[tys90]

A defective window may only be half the equation, how the window was installed and the quality of that installation is the other half.

 

[KiwiMace]

The problem with deflecting the air away is that in winter, you need the heating to run up the glass. Can you flip the grating around?

My vote is that the windows are defective. This installation is not exactly new technology.

Is the dodgey window company saying cold air or the hot air is damaging the seals?

 

[smb4050]

The window company has said the air shouldn't be blowing on the windows, period. My recollection from past experience is conditioned air shouldn't be blown across insulated glass because it stresses the seal which reduces the seals service life. In my original post I wrote there are already cracked interior panes of glass. There are several windows with condensation (20% +/-) w/4 already cracked out of 90 windows. 3 of those cracked this past winter. The building is located in NW Iowa. Thanks for sharing your comments and thoughts.

 

[AbbyNormal]

This sounds like "the dog ate my homework"

The way we build has a far greater impact on our comfort, energy consumption and IAQ, than any HVAC system we install

 

[AbbyNormal]

meaning the window mfg is coming up with a lame excuse

The way we build has a far greater impact on our comfort, energy consumption and IAQ, than any HVAC system we install

 

[ChasBean1]

Air blows up, about a foot from the glass and not on the glass directly. What you're seeing is a result of some other whole building phenomenon that will involve understanding of systems and controls. You should hire a consultant who knows what they are doing.

 

[smb4050]

I agree they need to hire a consultant who can provide more insight on the cause of the problem, but do they hire a fenestration/window expert or a mechanical expert? I'll recommend a window expert. Regarding ChasBean1's comment about it whole building phenomenon. I partially agree in that there could be multiply factors causing the windows to crack and lose their seal. What I don't understand is why the original windows lasted 20+ years before condensation caused their replaced? The attached picture is a exterior view of the installation.

 

[ChrisConley]

Where is the air coming from that 'blows' on the windows and wrecked them?

I've been blowing air on glass for years and never once had a manufacturer complain.

Has the air handling system changed recently: upgraded, replaced components, energy audit? If the air coming from the diffuser changed (to a warm humid airstream?) I could picture the airflow adding to a condensation problem, but typically the exact opposite is true.

 

[smb4050]

The HVAC system has not changed since the IG units were installed. If anything has changed is the thermostats are set cooler in the winter and warmer in the summer.

The condensation is between the panes of glass, so the condensation is apparently due to the perimeter seal failing.

Thanks for the reply and comments.