That is a very interesting question. When considering any building science inspired project, we need to balance between many imperfect options.
Please bear with me.
- The first question to ask about a duct system is..how tight can I make it? This is because leaky duct systems pull in polluted air from attics/crawls/walls and end up providing less comfort for more money.
- The second question to ask is...how durable and healthy can I make the materials? This is where you consider plastic vs. sheet metal or mastic vs. EcoSeal or gasketed filter boxes vs. cheap filters or...
- The third question is...how do I insulate and properly install this system? This is where you consider furnace location, reducing duct length (less materials and better airflow), insulation style, etc.
There are always many more questions, but the last critical question is...how do I put all three questions above into a cost-effective and feasible project in my home? This is where I will try to answer your question directly in light of the above considerations. The answer is maybe.
- I mean, I didn't expect kids toys to be poisoned with lead so I supposed anything is possible.
- However, even if the plastic in the heat exchangers and ducting presented any health risk, the other benefits of an HRV far outweigh the risk of plastic use.
- For instance, an HRV (if designed and installed correctly) will provide sufficient air exchange so that you are not pulling attic/crawl air into your home.
- In addition, you will be actively exhausting stale air, CO, moisture, Radon, or whatever else may exist.
If a plastic duct system is able to be installed cheaper, tighter, shorter, and with better insulation then it is probably a good idea. The whole point is to limit air leakage into conditioned space while providing fresh control air.
The bottom line is that an HRV (or ERV) is always a good investment for a home and don't let plastic stop you from installing one.
However, if you are 100% installing an HRV, but thinking about upgrading to sheet metal (or other non-plastic duct), then it may be worth looking into the cost.