Join the MRA | Member Login
Find a Professional
Sign Up Log In Add New Topic

TOPIC: Condensation Issues

Condensation!!!!!!

Return to Condensation Issues

Return to Archive

Return to Forum

I have been installing MaxRib Ultra on my new house. Yesterday morning i was out bright and early in the 30 deg. temperature. When I went up to the ridge cap, I noticed it looked like it was raining on the bottom side of the metal!!!! The sun just came out and was hitting it. I installed it over 1X4 2' on center over existing roof and put in a vented ridge. What's the deal- this isn't good....... ;(
Guest User

11/10/2003
This is a very common question on this site at this time of the year. Your message is somewhat confusing in that you say it is a new house but you are installing over an existing roof. Assuming that you recently purchased the house and that you are installing a new roof over the existing asphalt shingles on 1x4 at 24" centres. You would have then cut the ridge open for the attic to breath. In doing this you need to check your soffit vents and do a calculation on the free area they provide, then match the ridge ventilation to it while ensuring it meets the 1/300 ratio in the building code of ceiling area to total ventilation. Moving on to your concerns. This is a normal occurrance with any roofs, you just see it more with metal. Any condensation that does form to the underside will hang there. If it gets too much it will run down the underside of the cap and out onto the sheets below. I suspect that you may have excess moisture in the roof assembly. The new 1x4 that you added will have high moisture content and as the 1' air space heats and cools will slowly release the moisture over time however it will add to the condensation. Next is that if you put an new addition on, then the moisture levels are even greater for the first year as the wood dries. Eventually it becomes a sponge somewhat and helps control condensation. I would be most concerned over the soffit ventilation to ensure that it is adequate. If you have provided too much ridge ventilation and say if there was existing gable ventilation, you will have short circuiting of the air which changes with the major swings in air temperature at this time of the year. Hope this helps and if you have any further questions you could contact me directly. Good Luck.
Allan Reid
Dura-Loc Roofing Systems, Inc.

11/10/2003
Sorry- the house is new to me, but not a new build!! It has cathedral ceilings with 1X12 roof joists,r-30 insulation and air baffles from eave to ridge. The eave vents are continuous with about 2" cut away on each side of ridge. Is this something that will just kinda happen at this time of year and the right weather conditions?
Guest User

11/10/2003
The fall weather is a perfect time for condensation The daytime temperature is typically above the dew point, the air is moist with the rain and the temperature drops fast at night across the dew point. Hence condensation. I am assuming that styrofam air baffles were installed under the plywood prior to the instalation of the isulation. You say you have eaves vents however you may mean soffit vents. Regardless I would still identify the type and quantity, slip down to the local lumber yard and get the typical free air numbers and calculate what you have comming in. Then match the ridge to it or slightly more at best. If you do not have enough air at the eaves you have the opportunity to put a vented mesh closure under the metal at the eaves to vent the 1' space created by the strapping. By your description you have already vented this space from the ridge. The more you equal inside attic to outside temps the less dew point crossings and condensation. Sounds like you have a handle on it.
Allan Reid
Dura-Loc Roofing Systems, Inc.

11/11/2003
I have a condensation problem and would like to know what you think the problem is. I have steel decking, one sheet of 3" iso rigid board and a standing seam metal panel. The steel decking meets on different planes and is not lapped togather to form a 100% metal barrier. The interior has a suspened dry wall ceiling with large opening in it for lights to shine through yet be hid above the ceiling. The a/c returns are above the ceiling as well as below the ceiling making the interior envelope from the bottom of the steel decking to the floor. The decking is welded to the bar joist on 12" centers or thereabout. Only on cold, heavy frost mornings does it drip in the building. It drips from the welds and out the ends of the decking. There is no insulation on top of the ceiling. This is the exact makeup of the roof and ceiling nothing more nothing less. Whats your opinion. Thanks
Bruce Cowan

11/21/2003
Sounds like the bottom side of the metal deck is getting cold enough for warm moist air inside to condense on it. Normally, this could be addressed through ventilation but it doesn't sound like your situation lends itself too well to that. Is there by chance a lot of moisture inside the building which could be reduced in some fashion, perhaps even with a dehumidifier? Todd Miller
Todd Miller
Isaiah Industries, Inc.

11/21/2003
The moisture does not condense on the bottom of the decking. It drips out of the decking through weld holes and out the ends of the decking. The air is not moist in the space, 70 degrees and 18%RH when the dripping occurs.
Guest User

11/21/2003
As an old time commercial builder I think there may be more than one factor. I am assuming by your assembly description that it is a commercial standing seam product with stand off clips. It is then possible that the deck is off the insulation a little and as there is no air barrier and the deck full of holes, warm air is migrating up and condesating. As well it sounds like there is no moisture barrier then between the SS Roof and the insulation to catch the condensation which will move down through the joints and drip out the holes. While you have good dry air in the ceiling space there is no way to flow air in the deck flutes to dry it out.
Allan Reid
Dura-Loc Roofing Systems, Inc.

11/21/2003
Do you have another name for air barrier and would the air barrier have a permeance rating of 0.05 and where would you place it in this assembly.
Guest User

11/21/2003
The name Air Barrier refers to its purpose. Basically to stop warm (moist at times) interior air from migrating out through the ceiling assembly where it can condesate as it cools, sometimes still within the assembly and if cold enough freeze limiting the insulation values and causing damage to the assembly. Unfortunately I am converted to metric but I believe that any material less than .1 is acceptable. It all depends though on sealing all joints and penetrations. If you have identified the lack of an air barrier as the problem you could have the underside of the steel deck skinned with a thin layer of sprayed in place foam provided the assembly is not fire rated. Also there are some good closed cell foil faced materials that can be glued and tapedonto the ceiling that will add some insulation. Remeber though, that condensation forms from two sources, the warm inside air noted above, but also in the normal occurance with the air in the space under the metal. I would choose a typical bd day and have your contractor open up a section of roofing to investigate.
Allan Reid
Dura-Loc Roofing Systems, Inc.

11/24/2003
i have a new cabin and a metal roof system installed on it however it has a lot of condensation on the under side of the metal roof roof consist of metal roofing nailed on 24" strips of 1x4 . nailed on 2 x 10 inside there is a cathedral ceiling with tongue and groove white pine nailed under rafters 6 inches of insulation on top of tongue and groove and a vapor barrier nailed to rafters before tongue and groove was installed also ceiling flattens about 8 ft from top of apex of roof with same insulation on it can you tell me how to stop this? will a eave vent on each end of cabin help?
Guest User

11/28/2003
We just added a 2000 sqft. addition onto our house. We decided to go with a metal roof. We are having a bad problem with condensation. We added an upstairs and extended our house out the back and one side. They placed the metal roof on 1x4 attached to 2x6. The upstairs ceiling is sheetrock with 6" fiberglass insulation between it and the metal roof. The addition to the back of the house has a good bit of space between the roof and ceiling but the metal roof is sweating so bad that it is leaving small puddles of water on top of the insulantion laying on the ceiling. Please tell me what I need to do to correct this problem. Please let me know if I need to send more information. Thanks for all of your help!
Guest User

11/29/2003
You have part of the roof asembly correct from the inside out. You did not say which area you are from so I can not comment on the amount of insulation, however you are missing a couple of components in your sytem. Ventilation. The building code requires that you have a minimum of 1" in the USA and 1 1/2" ventilated air space over the insulation. It appears as if this has not been done. Underlayment. You are required by code to install a moisture barrier underlayment under the roof covering unless tested otherwise. It sounds like this has not been done either. Combined with the limited insulation you have a condensation coctail. You come to the cabin and crank up the heat. There may not be enough insulation to hold the heat back and as there air space is not vented, it condensates on the back of the roof metal, and as there is no moisture barrier, it will run down the underside until it hits the strapping and drips. I would get your co ntractor to correct the problem which may require removing and re installing the metal roof.
Allan Reid
Dura-Loc Roofing Systems, Inc.

11/30/2003
Please see may answer to the one above. It is truly unfortunate that everyone seems to be cutting costs out of the construction by elliminating the sheathing, underlayment and ventilation. Again depending on which climate you are in, you may not have enough insulation and you did not mention whether they put in an air barrier to the inside. If you need more help, contact me directly with more information.
Allan Reid
Dura-Loc Roofing Systems, Inc.

11/30/2003
I am putting a metal roof over 2x4 purlins that run horizonally, over 1" foam board with foil on both sides, over the wood trusses. Will this system minimize condensation? If not, will the 2x4's running horizonally keep the water from running down to the eaves? I will tape all seams with foil tape and install eave ventallation under all eaves and ridge vent entire cap. I live in South West Missouri which has high humidity in summer. Would it be necessary to install more insulation under the 1' foam? Thank You for your help
jim newton

11/30/2003
Truly I need more information as one must look at the entire roof asembly from the ceiling up. As well what is the buildings purpose, slope and type of roof material? If it is a home and you have vaulted ceilings, then you must provide 1" minimum of vented air space under the roof covering, over the insulation. If it is a vented ceiling assembly then there is little value in putting insulation down at this point in the assembly. Regardless you are required to put a moisture barrier down under the roof covering unless the manufacturer has tested without it and it is included in their product approval report. You will need to check with the insulation supply compant to see if they have tested their product taped as an underlayment. I suspect not. Regardless when you are installing on 2" strapping you have the space required for venting but not the air flow. You will need to strapp vertically first over the rafters and then horizontally. Use a 30# felt over the insulation and vented profile strips at the eaves and ridge.
Allan Reid
Dura-Loc Roofing Systems, Inc.

12/1/2003
We have a new house with a standing seam roof in down east maine. The roof is built with 2x10 rafters with 5/8" plywood. It was covered with grace ice and water shield. The inside has r-40 fiberglass insulation with raftermate. it is a catherdial ceiling and we are getting alot of condensation when the temp changes just a couple of degrees. we had a ridge vent and it seemed to make it worse.what do we do.
Guest User

1/26/2004
I am building a timberframe home and plan to have a metal roof. Using t & g aspen for the roof sheathing, foam panels with osb on top with 30lb felt covering. Do I need to create a space between felt and metal roof? What about venting? Any guidance would be appreciated. Thanks, Josh
Josh Sorrell

1/27/2004
We have a house built in the 70s with an asphalt roof and would like to install a metal roof. I have some doubts about our contractors inthis area. What basic questions do I need to ask him about the installation? Things like condensation, over existing shingles, extension over the roof extension. Also, the local supplier only guarentees 20 to 30 years. Thank you Tom Anderson
Guest User

1/27/2004
A few things... 1) I would have suggested a complete vapor barrier behind the drywall. 2) Do you have soffit vents and are you sure that the Raft-R-Mate is allowing complete airflow along the bottom side of the roof decking? You should have a bare minimum of 1" vented airspace with intake (soffit vents) and exhaust (ridge vent). 3) The ice and watershield is a non-breathable underlayment. Any moisture which gets into the attic cannot escape through it and will condense if it hits dewpoint. 4) Look for sources of excessive moisture inside the home and eliminate them. 5) Try running a dehumidifier.
Guest User

1/28/2004