Hello there,
I'd definitely encourage you to think about how you might go about getting some higher quality links to add in to the mix.
Guest posting (as Donnie suggested) would definitely be something that I'd encourage you to engage in, plus I really like your ideas for getting links from government / universities etc.
Something similar could also be applied if you were providing services for companies with websites.
Other opportunities might include:
Press release opportunities (either local or national).
- Do you have an interesting story to tell about a particular project you are working on? Are people in your company doing something for charity? Obviously it will need to be a genuinely good story in order to get coverage - but local press are often easier to engage with than national.
'Linkbait' Content
- Can you create some content to garner links? Perhaps something environment-related around window recycling or decreased heating bills? Or something around home improvement?
Competitions
- Could you run a competition to give something away? Doesn't necessarily have to be a full set of windows

Sponsorship
- Are there any local events that you could sponsor? This sort of thing can often result in both links from event websites, plus links from local press / other sites which cover the event.
Speaking at local events
- Similar benefits to sponsorship (see above).
I hope this helps,
Hannah