You need to address this with the lender and see if you can get that appraisal thrown out and a new one done. Arguing with appraisers is fairly futile. A single family rowhome should never be compared to twins or attached rowhomes but if the appraiser doesn't realize that (which is appraisal 101), you just want a new appraisal. The downside is that you'll have to pay for one and you're out the money for this one.
You can always change lenders too if this lender doesn't want to toss out the appraisal. (If you are doing an FHA loan, the appraisal can't be "tossed out".)... more
Pennsylvania has the PHFA program (Pennsylvania Housing Finance Agency) which offers lower interest rates, and in some cases downpayment and/or closing cost assistance. They are able to offer these programs through the sale of mortgage revenue bonds. I have provided a link to the site, below.