Maybe there's a better way, but you could always abandon the formRow
helper and manually display that input. E.g.:
<?php $emailField = $form->get('Email'); ?>
<input type="<?php $emailField->getType(); ?>" class="<?php $emailField->getClass(); ?>" placeholder="<?php $this->translate($emailField->getPlaceholder()); ?>" value="<?php $emailField->getValue(); ?>" <?php $emailField->getRequired(); ?> >
That gives you more control over how that input is displayed, but it's also laborious and error prone. Also I'm assuming you have a translation prepared in your .po files.