Any improvement in insulation will make a difference in comfort and energy costs if areas of need are addressed.
Most comfort problems, in a cold weather state, are the result of convective heat movement not conduction.Air leaks and/or convective loops result in unwanted drafts and reduced interior temperatures.
- As air in the home is heated it rises and creates a pressure in the upper levels of the home.
- As the air finds its way into the attic an equal amount of air is drawn into the house from areas below the high pressure line.
- The air going out is warm and the air coming in is cold, as cold as the outdoor air.
Your uninsulated north wall
The north wall of a building doesn't get any direct sun so it doesn't benefit from solar gain, thus it is colder than south, east or west facing walls. Insulating a north wall, by itself, probably won't make a big impact in the comfort level of your home. It may marginally reduce energy costs but the impact may be negligible.
If you want to improve the wall cavity insulation you could drill the exterior walls and fill cavities as you described in your inquiry. Unfortunately this process is not as effective as it sounds.
- Framing deficiencies, old insulation, wires, etc can prevent full cavity fills at proper densities.
- In older homes it could also lead to plaster damage if not monitored carefully.
While drilling holes from the exterior is the most common practice on existing buildings it is not uncommon to install through holes drilled from the interior of the home. This is especially intriguing in historic homes because it allows the contractor to monitor interior walls response to the increased wall pressure. Since you'll need to remove window and door trim to air seal common areas of leaks it might make sense to remove baseboard trim and drill a series of mid wall holes to complete the entire job from indoors. In either case it would be prudent to review the insulation installation with Infrared imaging to verify full cavity fill.
Reduce drafts to improve comfort
You can improve comfort in your home byreducing the unwanted draftsin your home.
- Hire a professional weatherization contractor (not necessarily an insulation contractor) to enter your attic and seal all penetration that might allow heated air to escape through your ceiling.
- This will immediately reduce the amount of air infiltration by volume and intensity.
- Additional improvement can be made by sealing the rough openings of doors and windows (by removing interior wood trim) and the rim/band joist area (if accessible).
Hire an independent energy auditor
Weatherization is typically a series of procedures rather than a single event.
Hiring an independent energy auditor to help you identify problem areas and possible solutions will allow you to map out a project that can be done in cost effective, high return on investment measures should be a priority.
Attacking comfort problems without understanding all of the causes and effects may result in great expense and minimal improvement. An independent energy audit may be the best money you spend.
For more information:
Read "I want to add wall insulation to my 1920 home. I have two locally available options -- Icynene and Tri-polymer foam. Can you advise me?" a Q&A answered by Alex Georgiou.