Expert: Bruce E. Johnson - 9/14/2010

Question
last year we had our garage turned into a bedroom. We left
the garage door in place so it wouldn't look like addition
although inside we framed it and put insulation drywall,
finished the wall to look like a regular wall. The room gets
very hot in the summer and very cold in the winter and
moisture. How should we fix the problem of being too cold or
to hot. I was told by a handyman that I should break the  
concert where the driveway starts to enter the garage. Is
that nessesary?  

Answer
Hi Linda, it sounds to me like you have more of an air conditioning and heating issue than anything else.  If your heating and air conditioning system was barely adequate for your existing house and then you add another four hundred square feet or so to the system it may not be able to heat and cool the new area adequately.  Also if you have no return air being pulled from the room into the air handler so that it can be conditioned properly then the air in the room will not change or circulate enough to heat or cool the area properly.  These reasons could account for the moisture and the hot and cold spots during the extreme seasons.  

As far as the concrete goes:  If you live in an extremely cold environment where temperatures remain at or below freezing most of the winter you may need a frost wall below grade to protect the garage slab on grade from the ground freeze.  As the ground outside freezes to a depth below the thickness of your garage footings then it is possible that the garage floor will then be sitting on top of frozen ground during the winter.  This is why many cold locales require foundations to reach a depth of three feet or so to get below the frozen soil and or require a frost wall to act as a barrier to freezing.  I have no idea how your particular garage foundation is built or how the slab is poured.  It would be unusual for the garage slab and the driveway to be poured together in one continuous piece.  Normally the garage slab is poured at one time during the construction of the house and the driveway is poured later upon completion of the house construction.  So I am not sure what the handyman is talking about.  Maybe your garage slab is built differently and it is all one piece.  I have no way of knowing based on your email.

One last thing.  You say you have insulated the walls etc.  Is the attic insulated?  Are any windows and doors insulated?  Were the existing walls insulated prior to the drywall being hung?  Or were they already drywalled when you built the bedroom?  It is possible that because the garage was built as a garage originally that the glass and exterior wall construction wasn't insulated properly to save on construction costs.  It could also be that the garage, since it was going to be a garage, does not have any vapor barrier under the slab which could account for moisture coming up from the floor.  Normal house slabs have visqueen under the concrete to keep this from happening. A simple gauge bought at a hardware store to measure humidity can be put in the room to check the room's humidity index.  If the humidity is above 55% then you need to bring it under control with a dehumidifier.  Normal humidity levels are 40-50% for comfort.  In the summer the humidity may go way up and in the winter it may go way down which could account for the hot and cold spots also.   

I guess that's about all I can say at this point.  Please feel free to write again regarding this or other matters, sincerely bruce e johnson..bejohnsonconsulting.com