Bad HVAC Install?
![](https://secure.gravatar.com/avatar/fc7b1f089a7422787836d67a577f9070?s=52&d=https%3A%2F%2Fimages.greenbuildingadvisor.com%2Fapp%2Favatars%2F200x200%2Fr.png&r=g)
A few fishy things with my HVAC install, wondering if any of these are real bad… my installers cut corners wherever they could.
1) The return air receive box (where my 2 return airs feed into – that connects to the furnace unit in the attic) is sealed to the unit on all sides (tape and paste), however the bottom seam of their connection is NOT sealed.
There is a lot of soot that looks like it went in thru there from my dirty attic. That is bad right? Or is that supposed to be open? I think it may be the cause of #2…
2) My vents (some more than others) have black soot stuff coming out of them. It is starting to build up on the ceiling even. Probably caused from #1?
3) 2 of my air receivers aren’t screwed in completely to the attic floor (room ceiling). Seems like air could escape there, but maybe not a big deal.
4) My air receivers are very tiny. 4″ ducts everywhere. He said that is the new “Green” initiative. Well, to me it doesn’t make ANY sense and it makes the ducts noisier.
5) My house during the day here in Texas (100 degrees) can’t get below 81. To my installers credit, I was supposed to have insulation in the house walls and floors by now, and my house is very leaky. All I could afford so far though is the closed cell in the attic.
THANKS! Right now I’m most worried about #1 and #2……
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
![](https://www.greenbuildingadvisor.com/app/themes/greenbuildingadvisor/dist/img/modules/detail-library/thumb1.png)
![](https://www.greenbuildingadvisor.com/app/themes/greenbuildingadvisor/dist/img/modules/detail-library/thumb2.png)
Replies
Ryan,
You should probably ask your HVAC installer to perform a Duct Blaster test and give you the leakage results. It sounds like your duct system is leaky. You should also ask whether the ducts were designed using Manual D.
For more information, see Duct Leakage Testing.
What's black and sooty in your attic? It sounds like it's being sucked into the return air plenum by negative pressure. All the ductwork should be completely sealed and insulated. Take Martin's suggestion a step further, and ask them to do the duct blaster test with theatrical smoke. You can call it good when the attic (and the rest of the house) doesn't fill up with smoke.
I have closed cell on the roof underside. THerefore the whole attic is open. The attic is mainly clean, but in the far side where I couldn't vacuum (by the unit) there was some dirt. However, the dust in the attic shouldn't get in because it is SUPPOSED to be a closed system (or so I think?). The gap as described in #1 means that the dust in the far side of the attic can bypass the clean part and the return filters, and just go straight into the unit where they forgot to tape the return air box connection gap.
Return air SUCKS in, and therefore is sucking in the dirt (and wouldn't expose any smoke test).
This is all just a theory of mine. I think my HVAC guy lies about stuff, so thought I would check with you guys. Same worries about the noisy small ducts, moisture on the receiving vents, etc.
When the blower is running, pressure on the return side is negative, pressure on the supply side is positive. Assuming there are no supply registers in the attic itself, attic air will get sucked into the returns if there are gaps in the installation, and it will take whatever dust and dirt with it. If those gaps are between the filter and the blower, then that dust will be circulated into your house.
Duct blaster testing involves sealing off all the registers and blowing a bunch of air into the ducts with a big fan (not the fan in the furnace). It creates positive pressure in all the ductwork, so if smoke is used it will come out any and all gaps, regardless of which side they are on.
Really, your best bet might be to hire someone else to do the duct sealing. Installers often don't have a clue about it, although they should.