Need advice on installing anchor bracket windows to AAC (autoclaved aerated concrete) in low voc manner
Last Post 21 Sep 2010 06:23 PM by woksawi. 12 Replies.
Printer Friendly
Sort:
PrevPrev NextNext
You are not authorized to post a reply.
Author Messages
woksawiUser is Offline
Basic Member
Basic Member
Send Private Message
Posts:116

--
10 Sep 2010 09:11 PM
We're building an autoclaved aerated concrete new home in Boulder, CO (7500 ft).  

We have anchor bracket windows fiberglass (double-pane heat mirror) that need to be mounted into AAC.   I have severe chemical sensitivities and, while I'm not worried as much about what goes on the exterior of the house, I'm trying to use the least toxic products and methods. 

Our crew has never worked with AAC or done green building.  We're doing a lot of the research.  The window company wasn't much help with suggestions, and the AAC company said to just use whatever works on concrete.

So with the anchor brackets, the crew is unsure exactly what to use to properly seal and attach the windows to the AAC, especially since the anchor brackets are also different from what they are used to (nailing fin) -- long story on that one.  Anyway,  they brought me a sample of a rubber primer as a suggestion (would wrap I guess from window to AAC blocks) and it was just nasty toxic.  It would probably off-gas but it made me wonder what else there is.

Anyway, the questions about the windows are:
- how best to attach anchor brackets to AAC blocks for Colorado mountain weather (I of course want to prevent any moisture coming in)
- if I don't want to use treated wood bucks, can we make the bucks out of AAC, or do we even need to? Could we screw directly into the AAC blocks?
- what is best green product that works on AAC/concrete to do the sealing?
- any way to do flashing with this situation?  (e.g. flexwrap apparently doesn't stick to AAC)
- what's the least toxic (VOC) caulk suggested for indoor use?  I've always used aquarium grade silicone for my caulk needs, but don't want to mess with window sealing.  I want to do that as well as it can be done.

On another note, could use an opinion on this situation, too.  Our windows were purchased a few years ago and then we had to put the project on hiatus (health and other issues).  They had been filled with krypton gas and were incredibly expensive.  The company stored the windows for us, and then we had them in the garage on our site for a year.  We didn't know about crimping until too late, and the company never told us anything, nor did they crimp the windows during storage.  Bottom line - the gas is gone.  A new company took over the old company and said they won't do anything to fix the situation or credit us.  It sucks.  Is the gas a huge loss?  Is it worth battling with this company (we have to get the windows in asap)?

Thanks for any help!
Jill
AltonUser is Offline
Veteran Member
Veteran Member
Send Private Message
Posts:2157

--
10 Sep 2010 10:16 PM

Jill,

Do the anchor brackets (metal I assume) already have holes in them for screws?  Will the exterior facade hide the brackets? 

I am familiar with Hebel AAC.  I think screws hold well in AAC.  Have you considered installings screws through the window jamb into the AAC to secure the windows?  Some windows without nailing fins already have holes in the jambs for screws.  Raise the bottom window and look for screw holes in the jamb.  If so, then with double-hung windows lower the top window to access the holes there.  

I do not see anchoring the windows to be much of a problem.  The problem is sealing the crack between the window jambs and the AAC since you may be sensitive to some chemicals.  You might be able to use low expansion foam and sealing tape from the outside to seal the windows.  If you do use sealing tape then apply it in the correct sequence. 

Residential Designer &
Construction Technology Consultant -- E-mail: Alton at Auburn dot Edu Use email format with @ and period .
334 826-3979
woksawiUser is Offline
Basic Member
Basic Member
Send Private Message
Posts:116

--
10 Sep 2010 11:10 PM
Thank you - yes they do have screw holes. The anchor brackets are on the side so I assume the facade would hide them. No holes in jams. Windows are sliders and casements.

We are also debating where ti put the windows - flush to outside or not. (Colorado mountain weather)

Does having a buck make the seal any better? If we can screw directly, wondering if there is any plus to adding aac bucks or not?

Do you have any suggestion for the "least toxic" expansion foam and a sealing tape that will stick to the AAC (you'd think this would be easy to find out but they are asking me to research)



BlackHatchUser is Offline
New Member
New Member
Send Private Message
Posts:50

--
11 Sep 2010 10:08 PM
You can attach to the concrete directly or set into a buck. I have seen steel bucks that were welded on site and installed. Pretty fabrication sensitive and probably overkill.

What is the exterior of the building going to be?

If the sill of the window is not slopped on its own, I would set the window in a pre-formed pan or on top of a piece of Azek that is ripped with a slope in it.

All the low-expansion foams are very non-toxic when cured. I think you will be fine. Flashing the head and jambs with a flashing tape is a plus depending on the exterior.

cmkavalaUser is Offline
Veteran Member
Veteran Member
Send Private Message
Posts:4324
Avatar

--
12 Sep 2010 07:56 AM
Posted By woksawi on 10 Sep 2010 09:11 PM
We're building an autoclaved aerated concrete new home in Boulder, CO (7500 ft).  


AAC company said to just use whatever works on concrete.


Thanks for any help!
Jill
Jill;

I am shocked at that response ; I would go back and verify that. Our experience withh AAC was contrary to that and they advised against certain anchors, in that they might "blow out" the AAC

Chris Kavala<br>[email protected]<br>1-877-321-SIPS<br />
woksawiUser is Offline
Basic Member
Basic Member
Send Private Message
Posts:116

--
12 Sep 2010 11:02 AM
Thank you.

The exterior is stucco.


woksawiUser is Offline
Basic Member
Basic Member
Send Private Message
Posts:116

--
12 Sep 2010 11:03 AM
The AAC company did say to use their fasteners, but for caulk/adhesives to use whatever works on concrete...
BlackHatchUser is Offline
New Member
New Member
Send Private Message
Posts:50

--
13 Sep 2010 12:30 AM
Flange, foam, and tape overtop.

Stucco over that and you are done.
woksawiUser is Offline
Basic Member
Basic Member
Send Private Message
Posts:116

--
13 Sep 2010 04:37 PM
So I just tested all the tapes and they are incredibly toxic (asphalt based). I know it will be under stucco, but any chance it would come into living space? It really made me sick. Are there any nontoxic varieties?
woksawiUser is Offline
Basic Member
Basic Member
Send Private Message
Posts:116

--
13 Sep 2010 06:45 PM
BTW - can't do nailing flange. We're stuck with the anchor brackets because it's a 4 week delay and we need to get windows in now. Plus the added expense to a company that has already screwed up a bunch and we don't want to give them even more money (e.g. they won't fix the gas that they put in the windows and is no longer there).
JellyUser is Offline
Veteran Member
Veteran Member
Send Private Message
Posts:1017

--
14 Sep 2010 08:11 AM
I have seen a lot of windows placed in AAC with anchors (never did it myself but watched). The windows had flush frames like replacement style (no flange). Set the window in the cut out, and place a pencil, marker or stylus through the screw hole in the window frame to mark the edge of the AAC where the hole should be drilled. Remove the window and drill the hole into the AAC just large enough to place the anchor. Put the window back in so it lines up with the holes, place the anchor through the hole in the window frame into the hole in the AAC as far as possible. The anchor looks like a long screw in a metal sleeve and operates like a concrete wedge anchor. Turn the screw and it expands inside the sleeve, putting enough pressure against the AAC to hold everything in place.

Then they used low expanding foam around the edges to fill any gaps. The windows were set in somewhat (walls were very thick) and would sit on a pre-formed metal pan which was sloped to the outside of the building envelope.
woksawiUser is Offline
Basic Member
Basic Member
Send Private Message
Posts:116

--
14 Sep 2010 06:58 PM
Thank you - great detailed descrip that will be very helpful.

They're not actually setting the windows in, but flush to the exterior (this was deemed best method to prevent water intrusion and deal with lack of real flashing apparently - not sure if I completely understand if flush is the best position, but that's what the current plan is).

Then they will be using Chemlink Novalink sealant to caulk it. 

And Chemlink M1 adhesive to do the flashing directly on the AAC. 

both are at www.greenbuildingsupply.com under caulks/sealants

These are supposed to seal well, work on AAC, and be ok for chemical sensitivities...according to Green Building Supply.  If anyone knows or thinks otherwise, please let me know asap.  I'm about to order these materials later tonight.

Thank you!
woksawiUser is Offline
Basic Member
Basic Member
Send Private Message
Posts:116

--
21 Sep 2010 06:23 PM
Do we need pans if we're setting flush to the outside? I wasn't planning on any...
You are not authorized to post a reply.

Active Forums 4.1
Membership Membership: Latest New User Latest: noooze New Today New Today: 1 New Yesterday New Yesterday: 0 User Count Overall: 34706
People Online People Online: Visitors Visitors: 139 Members Members: 1 Total Total: 140
Copyright 2011 by BuildCentral, Inc.   Terms Of Use  Privacy Statement