Steel Roofing vs Asphalt Shingles: An Environmental + Economic Trade-Off

I think of steel as being a "green" metal. I decided to analyze steel roofing versus the petroleum product asphalt shingles as used in roofing for a building after a recent trip to Perth. 

A steel roof is approximately twice the cost of an asphalt roof but lasts four times as long. But even with an 80-year life versus a 20-year life, it still does not quite make economic or environmental sense at today’s relative costs. 

Emotionally, I think metal roofs make a whole lot of sense. Steel roofs are generally for the life of the building, they have 40-year warranties, and with minimal care, they should last for over 100 years. So why then do they not have more market share? I decided to spend two days on this with our nIR equation, and come up with some answers. 

First off, steel roofs over asphalt shingle roofs have an ~0.84 nIR score, using the same inputs as we used for LED light bulbs last week (which scored 149 on the nIR scale when compared with incandescent bulbs). Thus, for every $10,000 more you invest into a steel roof (versus an asphalt shingle roof), expect to get a total environmental plus net present value economic return of ~$8,450. 

Let's start with the good parts (all of this in the linked model). If you put a steel roof on your house, during the life of that roof (1750 sq feet), you will save: 

• Six tonnes of roofing waste going to the dump, assuming a reasonably light asphalt shingle;
• Thirty net tonnes of CO2 production, both in the four asphalt roofs you aren’t installing, plus the energy savings from the lower heat consumption; 
• $80 a year of energy savings, with a present value of ~$1,000;
• Insurance savings; and
• Reduced fire risk.

The neatest thing is the energy savings from the reflection of less heat into the house. Asphalt roofs soak up the heat, while steel roofs, especially ones painted lighter colors, reflect the same heat. 

However, all of that is only worth $7,500, and ~$1,000 of that is in environmental savings.  

Why is it not more?

• Asphalt shingles are pretty inert when they are dumped into a landfill. They don't off-gas, they stay stable, and they act like a carbon sink. So the total environmental damage is limited to the refining, fabrication, and increased footprint of moving them around and dumping them. 
• Steel roofs have a super long life, but the present cost of three extra roofs starting in 20 years is only ~$5,000. So when you discount back the extra asphalt roofs, they are not that expensive today, and still cheaper than one steel roof. 
• Carbon is $20.00 per tonne in this model, but to get to an nIR value of 1, you need a $60 carbon price. 
• It costs way too much to install steel versus asphalt; if we wanted to shift this equation, dropping installation costs by just $1 per square foot would be a critical first step. Lang factors on steel roofs are just too high in North America. 

If I wanted to push steel roofs as an environmental solution, what would I focus on?

Standard roofing packages: figure out a software-hardware combination that scans a roof, and then sends the measurements to the steel factory to deliver a perfect solution. This will let you put up the roof with far less labor. Anything you do to get the Lang factors down by reducing onsite labor will make the wanted environmental savings far more realistic. 

Focus on hotter areas: From a cooling perspective, a steel roof in Miami, Florida, Perth Australia, or Phoenix is worth far more than a steel roof in Portland, Oregon. 

Pre-set up panels for solar: Design roofs such that there is a reduction in installation costs for solar panels on top of steel roofs versus asphalt shingles. Raised ridge metal roofs really should be optimal for mounting solar panels. The Lang factor on solar panels is the core driver for their suboptimal economics, and solar panels should be symbiotic with metal roofs. 

Trades training: Set up a lot of training for roofing contractors to install steel. The lack of skills in North America with steel versus asphalt is core to the increased installation price. I think Australia and the ROW have far more steel roofs for this reason alone. 

Conclusion: If steel roofs cost the same to install as asphalt roofs, there would be no asphalt roofing business left in North America. If carbon gets over $100 per tonne in real market pricing, we will also lose the asphalt roofing business. If the combination of those two things occurs, the steel companies could raise their prices significantly and still make money and deliver a quantifiable sustainable environmentally friendly solution.