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Insulating 100+ year old house

With the price of natural gas doubling over the past few years I am looking for the most cost effective way of insulating our circa 1895 Victorian house.
There is no insulation at all. The attic is completely floored with dimensional lumber. It also has knob and tube wiring. Insulating the attic would be difficult at best.
We have looked at insulating under the floor (the foundation is conventional) but I have heard that the knob and tube wiring should be replaced. Yard drainage is not the best and being in Mississippi the crawl space stays damp.
We also looked at various interior storm windows but have not found anything that seemed suitable. Exterior storm windows are not commonly used around here.
Thanks in advance.

Re: Insulating 100+ year old house

Insulating an old house would cause me some worry about interrupting the moisture transpiration through the walls. The moisture would collect in the insulation keeping the condensed moisture in contact with the framing. This could very easily cause the wood to rot over time. Moisture barriers are in older homes largely incomplete allowing water vapor into your wall cavity. This is ok without insulation. You would be best served by capping the attic with insulation where the water vapor can freely move without getting trapped and plugging up air infiltration around the windows, doors, baseboards and flooring. The other concern is covering over the knob and tube wiring causing the wires to overheat which could be a BIG problem. We had to remove our knob and tube before the insurance company would insure us against loss of our home. Good Luck.

Re: Insulating 100+ year old house

Best suggestion I can give, is to remove the knob wiring and update all of it. If the crawl space is large enough to have a guy crawl on his back, have it insulated with 2lb Closed Cell Foam. If you are doing a complete remodel of the home to where all the bones (studs) in the will be exposed, spray foam those as well. The attic will use the same insulation. When you reach a depth of 2” of Closed Cell Foam, the moisture barrier is built into the foam, but it has to be a minimum of 2”, not an average.

You will want to check with your local code but if they use the current 2006 IRC Book, the state of Mississippi will require you to have R-13 or 19 in the floor, R-13 in the wall, and a R-30 in the ceiling. Closed Cell Foam having an R-Value of 6.5-7 per inch you will have to have 3” installed in the walls, 4” in the floor – depending on your county - to achieve the 2” minimum, 5” in the ceiling. Also have the Spray Foam Contractor spray a couple of inches over all rafters touching exterior walls. This will help glue the roof down to the home.

You will also find that 2lb Closed Cell Foam is a FEMA Class 4 Flood Resistant Material. This will make your insurance company happy.

Class 4 is Resistant to floodwater damage. Materials within this class may be exposed to and/or submerged in floodwaters in interior spaces and do not require special waterproofing protection.

You will find this information if you do a search on Google for Class 4 Flood Resistant Material and click on the PDF link to the FEMA site.

The Closed Cell Foam will also add tremendous structural integrity to the building, so you have a little extra comfort in the case of a hurricane. The biggest bonus of using the foam to enclose the building envelope is the amount of money you will save on your annual energy bill.

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