Insulation over HVAC system in Attic

[dmccarty]

They DIY insulation blower thread pushed me to finally ask a question to the TBN Brain Trust.

Our HVAC system is in our attic. The heat pump is outside but all of the duct work and blowers are in the attic. Not a big deal except that in my area we are supposed to have R35ish in the attic. And we do. Except where they put down 4x8 sheets of OCB on the joists to install the HVAC. As a result there are huge "holes" in the insulation were we might have R15-R20. Under the 4x8 sheets that hold the HVAC, batt insulation was put into the joists, which is how I figured we have about R15-20.

This has bothered me since I saw the installation. But it was completed by the time I saw the work. I have had various idea on how to get more insulation around all of the big duct boxes. It seems like the simplest thing to do would be to just buy more batt insulation and just cover the duct boxes and blower(s).

Would covering up the duct distribution boxes and blower(s) with batt insulation be a problem? I figure the easiest, fastest, cheapest thing to do would be to just lay the batt insulation over everything.

Later,
Dan

 

[kenmac]

Would covering up the duct distribution boxes and blower(s) with batt insulation be a problem?

No. I have wrapped alot of duct work on the outside

 

[Willl]

Cover the duct work OK, I wouldn't cover the evap box.

I wonder what the R rating of OCB is ?

 

[dmccarty]

Cover the duct work OK, I wouldn't cover the evap box.

I wonder what the R rating of OCB is ?

The R value of OCB or plywood for that matter is not much. It depends on the thickness but its around .5 R.

Why not cover the evap box? That is a big hole in the insulation. Will the insulation stop the evap?

Thanks,
Dan

 

[kenmac]

covering the evap. box is ok. Just don't block your condensate drain. Or, you may have a flood

 

[dmccarty]

covering the evap. box is ok. Just don't block your condensate drain. Or, you may have a flood

The condensate drain is another sore spot. The drain ends up on the south side of our house which is the most visible side of the house. Its not the front of the house but its the most visible due to the drive way. So everyone gets to see it. And they just busted a brick to get the drain outside. The mason was not very happy. The good thing about the location is that since it IS so visible its easy to check to make sure its draining correctly and not backing up in the pan in the attic.

I check the pan every year for any sign of back up and so far so good!

Sounds like I can do the insulation. While up in the attic I'm going to build up the joists so I can lay down some flooring to walk on. The inspector at the very last minute required a walk way. So the builder threw down the plywood over the joists which of course minimized the R value. I am going to rip that up, build up the joists so more insulation can go in and then put the plywood back down. And I need to expand the walkways while I'm at it.

Good excuse to finally buy the nail gun.

Thanks for the help,
Dan

 

[kenmac]

For back up (If you don't already have it) You can install a float seitch on the emergency drain pan( if you have 1 It should be a pan on the underside of the coil or the entire unit) wire it into the t.stat wires so, if your drain ever stops up it will shut the ac unit down. Always good to have a backup saftey for condensate drains

 

[Lasgambler]

In the homes I build in the Southwest, if we have a "split system" as you have described, We will build a platform 1 foot above the finish ceiling for the pan and hang the Air Handler from the trusses. Then we are able to blow insul. under the pan. This method also helps to eliminate any noise from the unit. Our code requires two condinsate drains, primary and secondary, the primary has to exit the home over a window so you can see it drip from the inside of the house.

 

[dmccarty]

For back up (If you don't already have it) You can install a float seitch on the emergency drain pan( if you have 1 It should be a pan on the underside of the coil or the entire unit) wire it into the t.stat wires so, if your drain ever stops up it will shut the ac unit down. Always good to have a backup saftey for condensate drains

Kenmac, they did install the switch.

Now I know what the switch does. Did not know if it killed the AC or triggered an alarm. Good to know it kills the AC since if that happens I know what to check after the breakers.

Thanks!
Dan

 

[dmccarty]

In the homes I build in the Southwest, if we have a "split system" as you have described, We will build a platform 1 foot above the finish ceiling for the pan and hang the Air Handler from the trusses. Then we are able to blow insul. under the pan. This method also helps to eliminate any noise from the unit. ....

This is how I thought it should be done but alas it was not. Funny that the electricians KNEW I was not going to be happy with what the HVAC guy did. They watched me looking at the HVAC installation to see my reaction. Not really happy but it was too late to tear it all out and start over.

Hopefully the chimney sweep will straighten the fireplace chimney this month. The HVAC guy did that one as well. The HVAC problems and a few things the framer did wrong are about all I can complain about on the house. So all in all I can't really complain too much at all. Got a really well built house that just needs some tweaking.

Later,
Dan