How To Give Your Home A Free Insulation Injection?
Nothing is for free these days – or is it? I needed to insulate a small kitchen which was very cold in the winter and hot in the summer despite having the recommended size of radiator and open windows in summer. Whilst I was toying with the idea of getting down to add insulation, my wife asked me what I wanted to do with all the plastic carrier bags we amass every shopping day.
I had seen free insulated shipping boxes consisting of inflated plastic bags looking something like giant bubble wrap and I wondered what the R value of plastic bags was.
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I am always thinking of recycling and plastic bags don’t pass me by in this matter so whilst I don’t regard myself as a horder, as soon as the shopping is decanted, the bags go straight into a much larger sack for use elsewhere at a later time, sometime, never.. Only in this case they proved to be of excellent value.
Giving The Walls The Sack (Of The Plastic Bag Kind)
The bags were in a much larger sack – hundreds of them. Then it hit me. Insulation depended on trapping air between the cold (or hot) surface and the usable area, ie. in the kitchen.
There are very very few genuinely new ideas and poly bag insulation was not one of them. The idea came to me but upon investigation, the Oregon University had already done a study on this and determined that
Polythene bags have many pockets of trapped air when crumpled so why not use them rather than disposing of them in the trash. It is also a benefit to the environment rather than burning or dumpng them in landfill.
A Chance To Try Free Insulation
The chance came when I replaced the old wooden window in the small kitchen with a modern uPVC double glazed version for the winter.
Removing the old window was very easy. If you have trouble knocking out a wood frame, just saw through it at one point and lever out the remains. If the new window is the same size, it will only need pushing in and wedging with a couple of wood wedges. Then check in all directions with a spirit level and spray foam it in there.
The New Windows
Polyurethane foam has a high strength when used for mounting windows and I have never needed to add screws or nails. They are virtually immovable once the foam has cured. It’s also helpful to take out the hinge pins and remove the opening panels as they are then so much lighter and easier to handle.
Having put the new window frame in place, wedged it and foamed it, making sure that the foam has cured, then we can put back the actual window panels but not before removing the protective tape on each of the sections. I’s easier at this stage.
I had decided to replace the internal window surrounds which were made purely from plasterboard. This gave me the opportunity to fill the voids with poly bags which made one hell of a difference to draught and cold
Putting In The Free Insulation
The next few ohotos show the void around the window filled with the old discarded bags. The internal walls consisted of steel framing with plasterboard, whilst the exterior is made from breeze-block. Time to add free insulation.
Open out the bags then lightly crush them and push them gently into the cavities. Don’t compress them too much as you need the air pockets within and between them to provide your insulation.
I pushed the lightly crumpled bags down into the void and continued until it was full. It’s amazing how many bags I found having collected them in sacks rather than sending them to landfill.
Heat Flow Analysis Summary
| Material | Heat Flow Index (HFI) | Calibrated Heat Flow Resistance | Performance Ratio | Equivalent R-Value |
|---|---|---|---|---|
| Empty Wall (No Insulation) | 0.55085 | N/A | N/A | N/A |
| R-13 Fiberglass Insulation | 0.43414 | 0.11671 | 1.00 (baseline) | 13.0 |
| Plastic Bags (Test Material) | 0.46621 | 0.08464 | 0.72518 (72.5%) | 9.43 |
Key Insights:
- Calibrated Heat Flow Resistance:
- This measures how much heat the material resists compared to the empty wall.
- Standard insulation resists 11.671% more heat than the empty wall.
- Plastic bags resist 8.464% more heat than the empty wall.
- Performance Ratio:
- Plastic bags resist 72.5% as much heat as standard R-13 insulation.
- Estimated R-Value for Plastic Bags:
- The plastic bags have an R-value of approximately 9.43, compared to the R-13 rating of fiberglass insulation.
It can be seen from the chart that the free insulation provided by old poly bags have a value of about 3/4 of that of fibreglass insulation which of course is not free. To my mind, this is well worth the little effort involved in stuffing them in there as free insulation. Although they arent inflated like bubble wrap, the air pockets are fairly small and numerous which brought my mind back to the free insulated shipping boxes.
Even on the day that I filled the gap with them, my wife walked into the kitchen and immediately remarked on both the new found silence and the extra warmth. I have some work to do on the kitchen ceiling at some time in the future and you can bet I will be collecting bags in the meantime as I know that both the kitchen ceiling and bathroom ceiling (both are extensions to the house), have no insulation whatever.
