HOW IMPORTANT IS A VAPOR BARRIER AND
WHAT TYPE OF BLOWN-IN INSULATION DO YOU RECOMMEND?

QUESTION FROM JAY SCOTTSVILLE, NY

Hello,

I saw your website in a search about insulation and was hoping you could assist me with a question.

I am getting blow-in insulation and am wondering about it without a moisture barrier. Is it a problem in old houses as mine was built in 1848 and has lath and plaster? One of my friends said getting the blown in fiberglass vs. cellulose is better as it isn't much more and it is not as prone to holding moisture. 

I am getting this done through a state program and they are paying for it but I like to be educated and don't want to do something that could potentially cause problems. They just informed me that they can only do the cellulose. The house currently has no insulation.

I look forward to any advice.

QUESTION #2:
Great; thanks for your time!  Also, does doing this without a moisture barrier really matter?

QUESTION #3:
Currently, there is not any central air but we do sometimes put 1 air conditioner in our bedroom window.  Are you basically saying considering this old house from 1848, it may not be a good idea to get the insulation as there is not anything but mineral siding, plaster and lath?

Sorry to keep asking questions! 

ANSWER FROM THE INSULATION DOCTOR:

Hello Jay,
 
With regard to your question as to what type of insulation I would recommend, I have two recommendations.  

If you are insulating the outside walls, it has been my experience that cellulose provides a higher R-factor in a wall cavity than fiberglass due to the fact that it packs more solid. 

On the other hand, if you insulating an open ceiling, I generally recommend using fiberglass.  You can help to overcome the lack of a vapor barrier by adding additional inches of insulation to the ceiling.  For example, if you are planning on installing an R-38 I would recommend raising the R-value by at least 10%.  

I hope this answers your question.

ANSWER #2:
Absolutely.  The technical jargon is called a "perm factor".  When this really comes into play is when you are trying to control humidity such as in the summer or in the extreme cold. 

In the summer, without a vapor barrier, you will literally be pulling humidity thru the insulation when your air conditioner working forcing your air conditioner to work harder to control the humidity.  

In the winter time the lack of a vapor barrier makes it harder to control the humidity inside the house and it becomes dry.  A higher humidity makes the house more comfortable at a lower temperature in the winter.  This is under ideal conditions and normally can only be achieved with new construction.
 
Hope this helps you to understand why a vapor barrier is important.

ANSWER #3:
There seems to be some misunderstanding.  Adding  insulation to your particular home will most likely cut your heating and cooling costs in half and will also make your home more comfortable to live in.  

I did not mean to discourage you from insulating your home.  I was just trying to address the issue of no vapor barrier.  The lack of a vapor barrier would cause your heating and cooling bill to be slightly higher -- maybe 3 to 5% maximum, but the added insulation will lower it many times over.
 
Bruce Jones
The Insulation Doctor