As requested; here is the def for skylights.
be aware that there is code working on this as well. Please download the mod yourself and test it.


<ThingDef Name="BasedSkyLight" Abstract="True">
<label>SkyLight</label>
<description>Lets in daylight through a window in the roof.</description>
<thingClass>Dubs_Skylight.Building_skyLight</thingClass>
<blockLight>false</blockLight>
<holdsRoof>false</holdsRoof>
<graphicData>
<texPath>Things/Building/skylight</texPath>
<graphicClass>Graphic_Single</graphicClass>
<shaderType>Transparent</shaderType>
<drawSize>(1.0,1.0)</drawSize>
</graphicData>
<category>Building</category>
<soundImpactDefault>BulletImpact_Metal</soundImpactDefault>
<drawerType>MapMeshAndRealTime</drawerType>
<terrainAffordanceNeeded></terrainAffordanceNeeded>
<repairEffect>Repair</repairEffect>
<filthLeaving>Filth_RubbleBuilding</filthLeaving>
<tickerType>Rare</tickerType>
<fillPercent>0</fillPercent>
<altitudeLayer>Weather</altitudeLayer>
<passability>Standable</passability>
<selectable>false</selectable>
<leaveResourcesWhenKilled>false</leaveResourcesWhenKilled>
<rotatable>true</rotatable>
<statBases>
<MaxHitPoints>80</MaxHitPoints>
<WorkToBuild>135</WorkToBuild>
<Flammability>0</Flammability>
<Beauty>5</Beauty>
</statBases>
<placeWorkers>
<li>Dubs_Skylight.PlaceWorker_Skylight</li>
</placeWorkers>
<building>
<blueprintGraphicData>
<texPath>Things/Building/skylightBP</texPath>
</blueprintGraphicData>
<isInert>true</isInert>
<isEdifice>false</isEdifice>
<canBuildNonEdificesUnder>true</canBuildNonEdificesUnder>
</building>
<clearBuildingArea>false</clearBuildingArea>
<designationCategory>skylights</designationCategory>
</ThingDef>

<ThingDef ParentName="BasedSkyLight">
<defName>SkyLightA</defName>
<label>SkyLight</label>
<graphicData>
<drawSize>(1,1)</drawSize>
<texPath>Things/Building/skylight</texPath>
</graphicData>
<drawStyleCategory>Default1D</drawStyleCategory>
<costList>
<GlassPane>1</GlassPane>
</costList>
</ThingDef>

<ThingDef ParentName="BasedSkyLight">
<defName>SkyLightD</defName>
<label>SkyLight 2x2</label>
<graphicData>
<drawSize>(2,2)</drawSize>
<texPath>Things/Building/skylight3x3</texPath>
</graphicData>
<size>(2,2)</size>
<costList>
<GlassPane>2</GlassPane>
</costList>
</ThingDef>

<ThingDef ParentName="BasedSkyLight">
<defName>SkyLightB</defName>
<label>SkyLight 3x3</label>
<graphicData>
<drawSize>(3,3)</drawSize>
<texPath>Things/Building/skylight3x3</texPath>
</graphicData>
<size>(3,3)</size>
<costList>
<GlassPane>3</GlassPane>
</costList>
</ThingDef>

<ThingDef ParentName="BasedSkyLight">
<defName>SkyLightC</defName>
<label>SkyLight 1x4</label>
<graphicData>
<drawSize>(1,4)</drawSize>
<texPath>Things/Building/skylight1x4</texPath>
</graphicData>
<size>(1,4)</size>
<rotatable>true</rotatable>
<costList>
<GlassPane>2</GlassPane>
</costList>
</ThingDef>